Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Pile Replacement Project, 30130-30139 [2011-12769]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 76, Number 100 (Tuesday, May 24, 2011)]
[Notices]
[Pages 30130-30139]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-12769]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XA116


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to a Pile Replacement Project

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

ACTION: Notice; issuance of an incidental harassment authorization.

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SUMMARY: In accordance with the regulations implementing the Marine 
Mammal Protection Act (MMPA) as amended, notification is hereby given 
that NMFS has issued an Incidental Harassment Authorization (IHA) to 
the U.S. Navy (Navy) to incidentally harass, by Level B harassment 
only, five species of marine mammals during pile driving and removal 
activities conducted as part of a pile replacement project in the Hood 
Canal, Washington.

DATES: This authorization is effective from July 16, 2011, through July 
15, 2012.

ADDRESSES: A copy of the IHA and application are available by writing 
to Michael Payne, Chief, Permits, Conservation and Education Division, 
Office of Protected Resources, National Marine Fisheries Service, 1315 
East-West Highway, Silver Spring, MD 20910.
    A copy of the application containing a list of the references used 
in this document may be obtained by writing to the above address, 
telephoning the contact listed here (see FOR FURTHER INFORMATION 
CONTACT) or visiting the internet at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications. Supplemental documents, including 
the Navy's Environmental Assessment and NMFS' associated Finding of No 
Significant Impact, prepared pursuant to the National Environmental 
Policy Act (NEPA), are available at the same site. Documents cited in 
this notice may be viewed, by appointment, during regular business 
hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Ben Laws, NMFS, Office of Protected 
Resources, NMFS, (301) 713-2289.

SUPPLEMENTARY INFORMATION:

Background

    Section 101(a)(5)(D) of the MMPA (16 U.S.C. 1371(a)(5)(D)) directs 
the Secretary of Commerce (Secretary) to authorize, upon request, the 
incidental, but not intentional, taking by harassment of small numbers 
of marine mammals of a species or population stock, by United States 
citizens who engage in a specified activity (other than commercial 
fishing) within a specified geographical region if certain findings are 
made and a notice of a proposed authorization is provided to the public 
for review.
    Authorization for incidental taking of small numbers of marine 
mammals shall be granted if NMFS finds that the taking will have a 
negligible impact on the species or stock(s), and will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses (where relevant). The authorization must 
set forth the permissible methods of taking, other means of effecting 
the least practicable adverse impact on the species or stock and its 
habitat, and monitoring and reporting of such takings. 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 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 small numbers of marine mammals. Within 45 days of the 
close of the public comment period, NMFS must either issue or deny the 
authorization.
    Except with respect to certain activities not pertinent here, the 
MMPA defines ``harassment'' as:

Any act of pursuit, torment, or annoyance which (i) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild [Level A harassment]; or (ii) has the potential to disturb a 
marine mammal or marine mammal stock in the wild by causing 
disruption of behavioral patterns, including, but not limited to, 
migration, breathing, nursing, breeding, feeding, or sheltering 
[Level B harassment].

Summary of Request

    NMFS received an application on December 16, 2010, from the Navy 
for the taking of marine mammals incidental to pile driving and removal 
in association with a pile replacement project in the Hood Canal at 
Naval Base Kitsap in Bangor, Washington (NBKB). Vibratory and impulsive 
pile driving and vibratory and pneumatic chipping removal operations 
associated with the pile replacement project have the potential to 
affect marine mammals within the waterways adjacent to NBKB, and could 
result in harassment as defined in the MMPA. This pile replacement 
project will occur between July 16, 2011, and July 15, 2013, with this 
IHA covering the first year of work. Six species of marine mammals may 
be present within the waters surrounding NBKB: Steller sea lions 
(Eumetopias jubatus), California sea lions (Zalophus californianus), 
harbor seals (Phoca vitulina), killer whales (Orcinus orca), Dall's 
porpoises (Phocoenoides dalli), and harbor porpoises (Phocoena 
phocoena). These species may occur year-round in the Hood Canal, with 
the exception of the Steller sea lion. Steller sea lions are present 
only from fall to late spring (November-June), outside of

[[Page 30131]]

the project's in-water work timeline (July 16-October 31). 
Additionally, while the Southern Resident killer whale (listed as 
endangered under the Endangered Species Act [ESA]) is resident to the 
inland waters of Washington and British Columbia, it is not found in 
the Hood Canal and was therefore excluded from further analysis. Only 
the five species which may be present during the project's timeline may 
be exposed to sound pressure levels associated with vibratory and 
impulsive pile driving, and were analyzed in detail in NMFS' analysis 
of this action.

Description of the Specified Activity

    In accordance with regulations implementing the MMPA, NMFS 
published notice of the proposed IHA in the Federal Register on 
February 4, 2011 (76 FR 6406). A complete description of the action was 
included in that notice and will not be reproduced here.
    NBKB is located on the Hood Canal approximately 20 miles (32 km) 
west of Seattle, Washington, and provides berthing and support services 
to Navy submarines and other fleet assets. The Navy proposes to 
complete necessary repairs and maintenance at the Explosive Handling 
Wharf 1 (EHW-1) facility at NBKB as part of a pile replacement 
project to restore and maintain the structural integrity of the wharf 
and ensure its continued functionality to support necessary operational 
requirements. The EHW-1 facility has been compromised due to the 
deterioration of the wharf's existing piling sub-structure. The project 
includes the removal of the fragmentation barrier, walkway, and 138 
steel and concrete piles at EHW-1. Of the piles requiring removal, 96 
are 24-in (0.6 m) diameter hollow pre-cast concrete piles which will be 
excised down to the mud line. An additional three 24-in (0.6 m) steel 
fender piles, and thirty-nine 12-in (0.3 m) steel fender piles, will be 
extracted using a vibratory hammer. Also included in the repair work is 
the installation of 28 new 30-in (0.8 m) diameter steel pipe piles, the 
construction of new cast-in-place pile caps (concrete formwork may be 
located below Mean Higher High Water [MHHW]), the installation of the 
pre-stressed superstructure, the installation of five sled-mounted 
cathodic protection (CP) systems, and the installation or re-
installation of related appurtenances.
    The removal and installation of piles at EHW-1 is broken up into 
three components described in detail below and depicted in Figure 1-3 
of the Navy's application. The first component of this project will 
entail:
     Removal of one 24-in diameter steel fender pile and its 
associated fender system components at the outboard support;
     Installation of sixteen 30-in diameter hollow steel pipe 
piles;
     Construction of two cast-in-place concrete pile caps, to 
be situated on the tops of the steel piles located directly beneath the 
structure in order to function as a load transfer mechanism between the 
superstructure and the piles; and
     Installation of three sled mounted passive CP systems, 
banded to the steel piles to prevent corrosion.
    The second component of this project will require:
     Removal of two 24-in diameter steel fender piles at the 
main wharf and associated fender system components;
     Installation of twelve 30-in diameter hollow steel pipe 
piles;
     Construction of four concrete pile caps;
     Installation of a pre-stressed concrete superstructure, or 
concrete deck of the wharf;
     Installation of two sled mounted passive CP systems; and
     Installation or re-installation of related appurtenances.
    The final component of this project will be:
     Removal of the concrete fragmentation barrier and walkway, 
likely by cutting the concrete into sections (potentially three or four 
in total) using a saw, or other equipment, and removal using a crane; 
and
     Removal of the piles supporting the fragmentation barrier, 
including:
    [cir] Thirty-nine 12-in diameter steel fender piles
    [cir] Ninety-six 24-in diameter hollow pre-cast concrete piles cut 
to the mud line.
    Vibratory driving will be the preferred method for all pile 
installation, and vibratory methods will be used for removal of all 
steel piles. Concrete piles will be removed with a pneumatic chipping 
hammer or another tool capable of cutting through concrete. The 
concrete debris will be captured using debris curtains/sheeting and 
removed from the project area. During pile installation, depending on 
local site conditions, it may be necessary to drive some piles for the 
final few feet with an impact hammer. This technique, known as 
proofing, may be required due to substrate refusal. As a result of 
consultation with USFWS under the ESA, impact pile driving, if required 
for proofing, will not occur on more than five days, and no more than 
one pile may be proofed in a given day. Further, impact driving or 
proofing will be limited to 15 minutes per pile (up to five piles 
total). During previous repairs at EHW-1, no use of impact driving has 
been required to accomplish installation. All impact driving will be 
conducted with the use of a sound attenuation device (e.g., bubble 
curtain) to minimize in-water noise.
    Vibratory pile driving is restricted to the time period between 
July 16 and October 31, while impact driving would only be performed 
between July 16 and September 30. Non-pile driving, in-water work can 
be performed between July 16 and February 15. The Navy will monitor 
hydroacoustic levels, as well as the presence and behavior of marine 
mammals during pile installation and removal. In total, twenty-eight 
30-in steel piles will be installed and 138 piles, steel and concrete, 
will be removed.
    The Navy estimates that steel pile installation and removal will 
occur at an average rate of two piles per day. For each pile installed, 
the driving time is expected to be no more than 1 hour for the 
vibratory portion. Impact pile driving, when required, will be limited 
to a maximum of five piles, with no more than one pile driven in a 
given day and no more than 15 minutes per pile. Steel piles will be 
extracted using a vibratory hammer. Extraction is anticipated to take 
approximately 30 minutes per pile. Concrete piles will be removed using 
a pneumatic chipping hammer or other similar concrete demolition tool. 
It is estimated that concrete pile removal could occur at a rate of 
five piles per day maximum, but removal will more likely occur at a 
rate of three piles per day. It is expected to take approximately 2 
hours to remove each concrete pile with a pneumatic chipping hammer. 
For steel piles, this results in a maximum of two hours of pile driving 
per pile or potentially 4 hours per day. For concrete piles, this 
results in a maximum of 2 hours of pneumatic chipping per pile, or 
potentially 6 hours per day. The total estimated time from vibratory 
pile driving during steel pile installation would be approximately 14 
days (28 piles at an average of two per day). The total time from 
impact pile driving during steel pile installation would be 5 days 
(five piles at one per day). The total time from vibratory pile driving 
during steel pile removal would be 21 days (42 piles at an average of 
two per day). The total time using a pneumatic chipping hammer during 
concrete pile removal would be 32 days (96 piles at an average of three 
per day).

[[Page 30132]]

    For pile driving activities, the Navy used NMFS-promulgated 
thresholds for assessing pile driving and removal impacts (NMFS 2005b, 
2009). The Navy used recommended spreading loss formulas (the practical 
spreading loss equation for underwater sounds and the spherical 
spreading loss equation for airborne sounds) and empirically-measured 
source levels from other similar events, including impact driving 30-in 
(0.8 m) diameter steel piles, vibratory removal of 30-in steel piles, 
and removal of 24-in concrete piles with a jackhammer to estimate 
potential marine mammal exposures. Predicted exposures are outlined 
later in this document. The calculations predict that no injury, 
serious injury, or mortality would occur associated with pile driving 
or removal activities, and that 2,488 Level B harassments may occur 
during the pile replacement project from underwater sound. No incidents 
of harassment were predicted from airborne sounds associated with pile 
driving.

Comments and Responses

    On February 4, 2011, NMFS published a notice of the proposed IHA 
(76 FR 6406) in response to the Navy's request to take marine mammals 
incidental to a pile replacement project and requested comments and 
information concerning that request. During the 30-day public comment 
period, NMFS received comments from the Marine Mammal Commission (MMC). 
The MMC's comments and NMFS' responses are detailed below.
    Comment 1: The MMC recommends that NMFS require the Navy to make 
careful observations in conjunction with in-air sound propagation 
information in order to add to the limited data available so that in 
the future thresholds for harassment due to airborne sound can be set 
based on more robust data.
    Response: NMFS agrees with the MMC about the importance of founding 
thresholds for behavioral harassment from airborne sound upon the best 
scientific information available, and about the importance of 
collecting additional data to improve that information. As described in 
the notice of proposed IHA, the Navy will be required to collect 
information regarding observed marine mammal behavioral responses to 
project activities, and if possible, the correlation to sound pressure 
levels. This information will be included in the Navy's monitoring 
report after completion of the pile replacement project.
    Comment 2: The MMC recommends that NMFS require the Navy to provide 
a full description of the survey methods used during shoreline surveys 
at NBKB, including how the Navy searched for animals, if and how it 
corrected its estimate for sighting probability, and if and how it 
corrected its estimate for decreasing sighting probability with 
distance from the observer.
    Response: The Navy has conducted two types of shoreline surveys at 
NBKB. The first set, which generated data used by the Navy in 
calculating density for California sea lions, are opportunistic visual 
and binocular area scans for marine mammals conducted by NBKB personnel 
from land at the NBKB waterfront. Sightings of marine mammals at 
manmade haul-out locations (e.g., piers) along the NBKB waterfront and 
in waters adjoining these locations are recorded. NBKB personnel 
attempt to conduct these surveys daily during a typical work week 
(i.e., Monday-Friday), although inclement weather or security 
constraints sometimes preclude surveying. Due to these constraints, the 
number of surveys conducted each month varies. During July-October (the 
period of in-water work for the pile replacement project), surveys have 
been conducted an average of thirteen times per month. Data recorded 
during these scans includes species, behavior, associated habitat, and 
weather, among other descriptive information. The majority of all 
sightings are of hauled-out individuals.
    No correction factor for sighting probability of California sea 
lions was used because there is no existing data to support it. The 
availability of a published study in which the movement of tagged 
animals was used in conjunction with aerial surveys allowed the Navy to 
use such a correction factor for harbor seals. The Navy did not correct 
for decreasing detection probability with distance because it would be 
atypical to do so for shoreline pinniped surveys. Correcting for 
decreasing sighting probability with distance is appropriate for at-sea 
surveys, typically targeted towards cetaceans. In addition, no 
information that could potentially support such a correction was 
collected during the surveys. Each shoreline and wharf location is at a 
different height above the surface; therefore, the distance surveyed 
offshore is different at each position, which would result in 
deviations in detection probability rather than a constant value. 
However, the area surveyed of nearshore waters adjoining manmade haul-
out locations is generally contained within the Waterfront Restricted 
Area (WRA), which extends approximately 500-1000 m offshore, and is 
generally able to be clearly observed.
    The second set of shoreline surveys conducted by the Navy, which 
generated data used by the Navy in calculating density for Dall's 
porpoise and harbor porpoise, were defined line transect surveys. 
Marine mammal surveys were conducted from a small vessel operating at a 
speed of approximately five knots. Surveys involved following pre-
determined transects parallel to the shoreline along the 3.5-mi (5.6 
km) waterfront. Transects were run from shallow water to deeper water 
with the first transect in each area located approximately 300 ft (91 
m) offshore. Additional parallel transects were located at 300-ft 
intervals out to 1,800 ft (549 m) from shore. During these surveys, the 
distance surveyed offshore generally encompassed the area out to the 
WRA, resulting in a total area of 3.9 km\2\ for each survey. Two 
observers and a vessel operator performed the surveys. Observers were 
trained in identification of marine mammal species and behavior, 
distance estimation, and area scanning techniques in order to reduce 
observer variation and avoid missed detections.
    While on transect, the two observers scanned from zero degrees off 
the bow to ninety degrees abeam on each side of the vessel. Observers 
scanned ahead of the vessel for diving mammals and communicated any 
wildlife detections to the other observer to minimize missed detections 
and avoid duplicate observations. Observers scanned continuously, not 
staring in one direction, with a complete scan taking about 4-8 
seconds. An observer focusing beyond 100 m is likely to miss some 
animals that are closer; thus, observers varied their focus from near 
to far fields in scanning within the 90-degree arc on each side of the 
vessel, and used binoculars only for species identification but not for 
sighting animals. To maintain effective transect width, animals 
detected through binoculars that would not otherwise have been detected 
with the naked eye were recorded in the comments field of the data form 
as being off transect. For each detection, time stamps were generated 
and location recorded with a GPS. In addition, the observers recorded a 
compass bearing and distance to each animal or group of animals at the 
point of first detection. Distances were measured with a laser 
rangefinder when possible. Number and species of animals and behavior 
at first sighting were recorded.
    Comment 3: The MMC recommends that NMFS require the Navy to (1)

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explain why it used the anticipated area of ensonification rather than 
surveyed area to estimate sea lion density and (2) correct the density 
estimate unless the Navy has a reasoned basis for not making such 
corrections.
    Response: The data employed in deriving a density estimate for 
California sea lions comes from the first set of surveys (shoreline 
surveys) described previously. NMFS has determined that these surveys 
provide the best available data for determining sea lion density. The 
other available dataset (defined line transect surveys) included only 
16 survey days in 2007-2008 during the time period in which the pile 
replacement project will occur (July-October); only six sightings of 
California sea lions were recorded during these 16 survey days. Two 
sightings were of individuals swimming, and the other four sightings 
were of groups of hauled-out animals. All observations of California 
sea lions during these surveys were over a mile away from the test pile 
location.
    Although the first dataset is limited in not having a defined 
survey area, as exists for the second dataset, the first dataset 
provides several years of data with many more data points for the 
months in which the pile replacement project is scheduled to occur and 
is thus the more robust source of data for estimating density of 
California sea lions. As described previously, the shoreline surveys 
averaged 13 survey days per month during July-October of 2008-2009, 
thus providing 104 data points compared with 16 for the line transect 
surveys. In addition, use of this more robust dataset results in a more 
conservative estimate for California sea lion density. The Navy also 
investigated published studies external to survey efforts at NBKB. 
Ideally, aerial surveys encompassing the local population's entire 
geographic range, used in conjunction with a correction factor for 
sighting probability, would be available, as was the case for harbor 
seals. However, this data is not available for California sea lions in 
Hood Canal.
    Because these surveys are of known manmade haul-out areas and 
adjoining waters, and are conducted from land, there is no appropriate 
way to define an area surveyed. It would not be appropriate to define 
survey area strictly as the area observed (i.e., the WRA) because the 
vast majority of sighted animals are hauled-out. At haul-outs, animals 
that forage over some greater area--unknown in this case--congregate in 
greater numbers than would be found in the absence of the availability 
of such habitat. Thus, a density calculated for animals found at known 
haul-outs and adjoining waters would not be applicable to the broader 
marine waters of the action area and would result in a gross 
exaggeration of sea lion numbers if extrapolated to that larger area. 
Because all of the California sea lion observations were of hauled-out 
individuals, which gives a reasonable proxy understanding of the 
numbers of animals that are utilizing waters in the vicinity of the 
project area for foraging, a reasonable method of generating a 
realistic in-water density would be to determine the approximate area 
that might be used by the animals when swimming and/or foraging. 
However, minimal data is available regarding the foraging home ranges 
of California sea lions. Research by Costa et al., (2007) regarding the 
foraging behavior of 32 adult females in California indicated that they 
travel an average distance of 66.3 +/- 11 km from rookeries. Data from 
Wright et al., (2010) for fourteen wintering males from the Columbia 
River indicate that travel is a maximum of 70 km from shore. Additional 
data for twelve adult males from mixed stocks in Washington showed a 
maximum travel distance of 99 km per day (Wright et al., 2010). Given 
these data regarding California sea lion travel during foraging trips, 
NMFS feels that using the maximum action area--the largest area 
affected by underwater sound produced by the action (i.e., 41.5 
km\2\)--as proposed by the Navy is an acceptable representation of the 
area in which these animals may be expected to forage in Hood Canal.
    In a previous environmental analysis for Dabob Bay, located in Hood 
Canal to the south of the action area, the Navy used published data 
(Jeffries et al., 2000) to produce a density estimate of 0.052 animals/
km\2\. While that was likely an underestimate, the density estimate 
produced by the methodology described here (0.410 animals/km\2\) is 
significantly higher, and thus more conservative. The density estimate 
is conservative in part because the Navy used the highest recorded 
daily values for each month in the dataset to estimate density. For 
example, in September 2009, the Navy used the highest recorded value of 
32 animals; the daily average for twelve surveys conducted that month 
was 6.75 animals. In addition, California sea lions are generally not 
present in the action area during July-August (one observed sea lion in 
51 survey days during July-August 2008-2009).
    It is possible that the data used, and the methodology used in 
estimating density, are not ideal. However, as described here, the data 
used is the best available, and the method of estimating density is the 
most appropriate based on available information. The density estimate 
is also likely conservative, as described here. Finally, no better 
information or alternative method of estimating density was provided or 
proposed to NMFS during the public comment period.
    Comment 4: The MMC recommends that NMFS require the Navy to re-
estimate the expected number of in-water and in-air takes for harbor 
seals using the overall density of harbor seals in Hood Canal (i.e., 
3.74 animals/km\2\).
    Response: As described in NMFS' notice of proposed IHA, the entire 
population of harbor seals in Hood Canal is estimated at 1,088 
(Jeffries et al., 2003). Using this estimate, with the entire area of 
Hood Canal (291 km\2\), produces a density estimate of 3.74 animals/
km\2\. This data represents comprehensive, dedicated aerial surveys 
that were conducted for harbor seals hauled out in the Hood Canal by 
the Washington State Department of Fish and Wildlife from 1978-1999. 
However, the work by Jeffries et al., (2003) used a correction factor 
of 1.53, based on VHF-tagging data (Huber et al., 2001), to account for 
seals in the water and not counted. The tagged animals were from the 
same populations that were surveyed aerially. The data from Huber et 
al., (2001) indicated that approximately 65 percent of harbor seals are 
hauled-out at a given moment (i.e., only 35 percent of seals are in the 
water at a given moment). The data loggers in these studies ran 24 
hours per day. These studies computed the average proportion ashore for 
all seals in the population assuming an annual basis; therefore, the 
data indicates that the percentage of harbor seals that can be in the 
water at any one time (35 percent) is assumed to be reasonably 
consistent on a daily basis for the entire year. As a result, exposures 
to underwater sound were calculated using a density derived from the 
number of harbor seals that are anticipated to be present in the water 
at any one time (35 percent of 1,088, or approximately 381 animals; 
1.31 animals/km\2\).
    There are a number of caveats associated with use of this data. The 
cited studies involved aerial surveys that were conducted primarily at 
low-tide, when maximum numbers of seals were hauled-out. However, the 
correction factor applied to determine the total population and take 
into account in-water harbor seals was not based on the aerial surveys 
but on VHF tag data which is unaffected by tidal influences. While some 
of the aerial surveys were conducted in Hood Canal, Huber et al.'s 
(2001) tagging data came from outside Hood Canal. The VHF data

[[Page 30134]]

came from radio tags deployed in three sites within the coastal stock 
and three sites within the inland waters stock to determine any 
regional haul-out variability. While Hood Canal was not specifically 
sampled in Huber et al.'s (2001) study, Jefferies et al. (2003)--Huber 
was an author on this study as well--found the VHF data broadly 
applicable to all inland water stocks and applied it to estimate the 
total population for the inland waters. While it is possible that 
proportions of harbor seals in the water versus on land in Hood Canal 
could deviate slightly from other inland water stock populations, it is 
unlikely that such deviation would be large. No similar site specific 
data exists for Hood Canal. Therefore, the data described here is 
considered the best available.
    It is possible that the density estimate used for estimating take 
may be an underestimate. Vibratory pile driving/extraction is estimated 
as occurring a maximum of four hours per day--with pneumatic chipping 
likely occurring a maximum of 6 hours in any day--and it is reasonable 
to expect that greater than 35 percent of the individuals in the action 
area would enter the water during the 4- to 6-hr duration of pile 
driving/removal. That is, assuming 65 percent of animals are hauled-out 
at a given time, it is possible that some animals may enter and exit 
the water during those four hours. Thus, while it is possible that no 
more than 35 percent of animals will be in the water at any given 
moment during pile driving, it is also possible that somewhat more than 
35 percent could potentially be exposed to underwater sound from pile 
driving during those 4 hours. However, no data exists regarding fine-
scale harbor seal movements within the project area on time durations 
of less than a day, thus precluding an assessment of ingress or egress 
of different animals through the action area. As such, it is 
impossible, given available data, to determine exactly what number of 
individuals above 35 percent may potentially be exposed to underwater 
sound. There is no existing data that would indicate that the 
proportion of individuals entering the water during pile driving would 
be dramatically larger than 35 percent; thus, the MMC's suggestion that 
100 percent of the population be used to estimate density would likely 
result in a gross exaggeration of potential take.
    In addition, there are a number of factors indicating that a 
density derived from 35 percent of the population may not result in an 
underestimate of take. Hauled-out harbor seals are necessarily at haul-
outs, and no harbor seal haul-outs are located within or near the 
action area. Harbor seals observed in the vicinity of the NBKB 
shoreline are rarely hauled-out (for example, in formal surveys during 
2007-2008, approximately 86 percent of observed seals were swimming), 
and when hauled-out, they do so opportunistically (i.e., on floating 
booms rather than established haul-outs). Harbor seals are typically 
unsuited for using manmade haul-outs at NBKB, which are used by sea 
lions. Primary harbor seal haul-outs in Hood Canal are located at 
significant distance (20 km or more) from the action area in Dabob Bay 
or further south (see Figure 4-1 in the Navy's application), meaning 
that animals casually entering the water from haul-outs or flushing due 
to some disturbance would not automatically be exposed to underwater 
sound; rather, only those animals embarking on foraging trips and 
entering the action area may be exposed. Moreover, because the Navy is 
be unable to determine from field observations whether the same or 
different individuals are being exposed, each observation will be 
recorded as a new take, although an individual theoretically would only 
be considered as taken once in a given day. If the estimated take is an 
underestimate (i.e., if authorized take is exceeded), there is the 
possibility that the Navy's action may need to be halted. Lastly, no 
alternative information or methodology was presented or proposed during 
the public comment period that would lead NMFS to believe that the 
MMC's recommendation would not lead to a gross exaggeration of 
potential take, or that would present a better estimate than that 
contained herein.
    Comment 5: Because the Navy did not request authorization for take 
of harbor seals resulting from exposure to airborne sound, the MMC 
recommends that NMFS require the Navy to shut down activities whenever 
a harbor seal is within the in-air Level B harassment zone (i.e., 
within a radius of 358 m).
    Response: The Navy's waterfront surveys have found that it is 
extremely rare for harbor seals to haul out in the vicinity of the test 
pile project area. While in-water sightings are fairly common, even 
temporary, opportunistic haul-out locations are limited within the 
acoustic zone of influence for airborne sound (maximum of 358 m) 
estimated for the pile replacement project. Harbor seal haul-out area 
can include intertidal or sub-tidal rock outcrops, sandbars, sandy 
beaches, peat banks in salt marshes, and manmade structures such as log 
booms, docks, and recreational floats. The lack of any of these 
suitable haul-out habitats in the immediate vicinity of the test pile 
project area makes it extremely unlikely that a harbor seal would be 
hauled out in range of sounds that could cause acoustic disturbance. 
The only structures within the largest airborne zone of influence (358 
m) are the current Explosive Handling Wharf (EHW-1) and Marginal Wharf. 
Both of these structures are elevated more than sixteen feet above the 
Mean Higher High Water (MHHW) mark, so there is no opportunity for 
harbor seals to haul out on these structures, even during the highest 
tides. Secondly, while a small intertidal/shoreline zone is present 
between these structures, it does not represent favorable haul-out 
habitat for the harbor seal. The shoreline located between the current 
EHW-1 and Marginal Wharf is extremely narrow, and is backed by a steep 
cliff face that is heavily vegetated with trees. Additionally, any 
portion of the intertidal zone that may be exposed at low tide is also 
vegetated with eelgrass beds and macroalgae, neither of which is known 
haul-out attractant for harbor seals. All harbor seals that are found 
swimming or diving within 358 m of the pile location would be 
considered to be taken by underwater sounds from pile driving 
activities; thus, there is no additional need to shutdown any time a 
harbor seal is within the airborne Level B harassment zone.
    Comment 6: The MMC recommends that NMFS encourage the Navy to 
consult with experts at the National Marine Mammal Laboratory to review 
and revise the Navy's survey methods as needed to make them 
scientifically sound.
    Response: The Navy has consulted with marine science experts in the 
past in the development of surveys and will continue to do so, 
including outreach with the National Marine Mammal Laboratory. NMFS is 
supportive of the Navy's effort to improve the strength of their survey 
design.
    Comment 7: The MMC recommends that NMFS require the Navy to record 
distances to and behavioral observations of animals sighted within the 
entirety of the in-water Level B harassment zone that would be 
established for vibratory pile driving and removal activities.
    Response: All shutdown and buffer zones will initially be based on 
predicted distances from the source, as described in the Navy's 
application. The size of the shutdown and buffer zones will be adjusted 
accordingly based on in-situ empirically measured received sound 
pressure levels. The 120-dB disturbance criterion for vibratory pile 
driving predicts an affected area of 40.3 km\2\. Due to financial and 
personnel constraints, it is impracticable to

[[Page 30135]]

effectively monitor such a large area. However, the 120-dB zone will be 
adjusted as necessary based on the results of in-situ hydroacoustic 
monitoring, and it is possible that the true 120-dB zone may be of a 
size that is practicable to monitor. Nevertheless, the Navy has 
committed to monitoring a minimum zone of 2,400 m, which corresponds to 
the width of the Hood Canal at the project site. This distance subsumes 
the next largest buffer zone (the 501 m, 90-dB harassment zone for 
airborne sound from impact pile driving). Observers will also be placed 
in additional locations within the 40.3 km\2\ vibratory disturbance 
zone, as indicated in the Navy's Marine Mammal Monitoring Plan. 
Sightings occurring in the area outside of the 2,400 m zone--the 
maximum zone in which it is practicable to effectively monitor--will 
still be recorded and noted as a take. However, it would not be 
possible to state with certainty that all takes were recorded, and 
fine-scale behavioral observations may not be possible. In addition, 
the proposed monitoring methodology is consistent with other actions 
analyzed by NMFS that involve prohibitively large harassment zones. 
These include seismic air gun and sonar activities, in which visual 
monitoring is only practicable for an exclusion zone corresponding to 
the injury thresholds and precise quantification of impacts to marine 
mammals within the behavioral harassment zones could not be empirically 
verified through visual observation, but was estimated by modeling.
    Comment 8: The MMC recommends that NMFS complete an analysis of the 
impact of the proposed activities together with the cumulative impacts 
of all the other pertinent risk factors affecting marine mammals in the 
Hood Canal area, including the Navy's concurrent wharf repair project, 
before issuing the authorization.
    Response: The pile replacement project and the test pile program 
overlap somewhat spatially and temporally. Spatially, the two areas are 
located adjacent to one another. There could be an overlap in their 
buffer zones (Level B harassment zones) but not for their exclusion 
zones (Level A harassment or injury zones) when the test piles closest 
to EHW-1 are installed and removed. Temporal overlap will occur as both 
projects will operate with a work window from July 16 through October 
31. However, for the test pile program impact pile driving will cease 
no later than October 14, and for pile replacement at EHW-1, impact 
pile driving will cease no later than September 30.
    The injury zones are not large enough to overlap spatially, and the 
Navy has agreed that no simultaneous impact driving will occur, in 
order to ensure that the combined energy of two impact rigs operating 
at once would not increase the potential injury zones. With regard to 
impact pile driving, EHW-1 is limited to impact pile driving only five 
piles per year, with a maximum of one pile driven per day and a maximum 
of 15 minutes of impact driving per pile. The test pile program is 
anticipated to require proofing for 18 test piles, although additional 
impact driving may be required should any of the piles fail to reach 
the necessary embedment depth with vibratory driving. Any impact pile 
driving during the test pile program would be limited to 100 strikes or 
15 minutes per day.
    No limitation has been placed upon vibratory pile installation and 
removal, as such limitation would significantly extend the length of 
each project's timeline and would result in a longer period of 
potential exposure for marine mammals in the Hood Canal. Vibratory pile 
drivers produce significantly lower initial sound pressure levels than 
impact hammers and are not known to cause injury to marine mammals. The 
simultaneous use of two vibratory drivers with similar sound outputs 
would likely increase initial sound pressure levels by approximately 
three decibels, thus increasing the potential area encompassed by the 
120-dB buffer zone (Level B harassment zone) from a modeled 100,000 m 
to 158,489 m, using the practical spreading loss model. As described in 
NMFS' notice of proposed IHA, these distances assume a field free of 
obstruction. However, Hood Canal does not represent open water 
conditions, and sound attenuates upon encountering land masses or bends 
in the canal. As a result, neither hypothetical area of potential 
behavioral effects is possible in the project area. The actual 
distances to the 120-dB behavioral disturbance threshold for vibratory 
pile driving will be significantly reduced due to the irregular 
contours of the waterfront, narrowness of the canal, and maximum fetch 
(furthest distance sound waves travel without obstruction) at the 
project area. Based on these factors, the concurrent use of vibratory 
hammers at both project locations will not result in any actual 
increase in the area encompassed by the 120-dB criteria.
    The Navy and NMFS have considered the potential overlap of these 
projects and the resulting effects that may occur, and have addressed 
these issues in the cumulative impacts analyses contained within their 
respective NEPA documents for these projects.

Description of Marine Mammals in the Area of the Specified Activity

    The marine mammal species that may be harassed incidental to 
estuary management activities are the harbor seal, California sea lion, 
killer whale, Dall's porpoise, and harbor porpoise. None of these 
species are listed as threatened or endangered under the ESA, nor are 
they categorized as depleted under the MMPA. NMFS presented a more 
detailed discussion of the status of these stocks and their occurrence 
in the action area in the notice of the proposed IHA (76 FR 6406; 
February 4, 2011).

Potential Effects of the Activity on Marine Mammals

    NMFS has determined that pile driving, as outlined in the project 
description, has the potential to result in behavioral harassment of 
California sea lions, harbor seals, harbor porpoises, Dall's porpoises, 
and killer whales that may be swimming, foraging, or resting in the 
project vicinity while pile driving is being conducted. Pile driving 
could potentially harass those pinnipeds that are in the waters 
adjoining the project site.
    Based on the analysis contained in NMFS' notice of proposed IHA, it 
is unlikely that this project will result in temporary or permanent 
hearing impairment or non-auditory physical or physiological effects 
for any marine mammal. Because this project involves driving a small 
number of piles, with limited use of an impact driver, and will occur 
in a small area for limited duration, effects to marine mammals are 
likely to be limited to behavioral harassment. The planned mitigation 
measures for this project (see the ``Mitigation'' section 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 will 
reduce or (most likely) avoid any possibility of hearing impairment.
    The effects of behavioral disturbance resulting from this project 
are difficult to predict, as behavioral responses to sound are highly 
variable and context specific. A number of factors may influence an 
animal's response to noise,

[[Page 30136]]

including its previous experience, its auditory sensitivity, its 
biological and social status (including age and sex), and its 
behavioral state and activity at the time of exposure. These behavioral 
changes may include changes in duration of surfacing and dives or 
moving direction and/or speed; changes in vocalization; visible startle 
response or aggressive behavior; avoidance of areas where noise sources 
are located; and/or flight responses. Pinnipeds may increase their 
haul-out time, possibly to avoid in-water disturbance. Since pile 
driving will likely only occur for a few hours a day, over a short 
period of time, it is unlikely to result in permanent displacement from 
the area. Temporary impacts from pile driving activities could be 
experienced by individual marine mammals, but would not be likely to 
cause population level impacts, or affect any individual's long-term 
fitness.
    The three cetacean species are rare in the project area, and, if 
present, numbers will likely be in single digits. While pinniped 
numbers will likely be greater, there are several factors indicating 
that these animals may only experience minor effects from behavioral 
disturbance. No haul-out areas are located in the immediate vicinity of 
the project site. California sea lions haul-out on manmade structures 
along the NBKB waterfront, typically over a mile from the project site. 
Harbor seals, though present in the Hood Canal year-round, have primary 
haul-outs even further away, in Dabob Bay to the west and at points 
further south.
Anticipated Effects on Habitat
    NMFS provided a detailed discussion of the potential effects of 
this action on marine mammal habitat in the notice of the proposed IHA 
(76 FR 6406; February 4, 2011). The pile driving activities at NBKB 
will not result in permanent impacts to habitats used directly by 
marine mammals, such as haul-out sites, but may have potential short-
term impacts to food sources such as forage fish and salmonids. There 
are no rookeries or major haul-out sites within 10 km (6.2 mi), 
foraging hotspots, or other ocean bottom structure of significant 
biological importance to marine mammals that may be present in the 
marine waters in the vicinity of the project area. Therefore, the main 
impact issue associated with the proposed activity will be temporarily 
elevated noise levels and the associated direct effects on marine 
mammals, as discussed previously in this document. The most likely 
impact to marine mammal habitat occurs from pile driving effects on 
likely marine mammal prey (i.e., fish) near NBKB and minor impacts to 
the immediate substrate during installation and removal of piles during 
the pile replacement project.
    Sound pressure levels of sufficient strength have been known to 
cause injury to fish and fish mortality (CALTRANS 2001; Longmuir and 
Lively 2001). However, due to mitigation measures in place to reduce 
impacts to ESA-listed fish--notably including adherence to the July 16-
October 31 work window--the most likely impact to fish from pile 
driving activities at the project area will be temporary 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 pile replacement project.

Mitigation

    In order to issue an IHA under Section 101(a)(5)(D) of the MMPA, 
NMFS must set forth the permissible methods of taking pursuant to such 
activity, and other means of effecting the least practicable adverse 
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.
    The Navy has established exclusion and buffer zones (Level A and 
Level B harassment, respectively), based on modeling described in NMFS' 
notice of proposed IHA (76 FR 6406; February 4, 2011). The Navy will 
implement the following measures for these zones:
     The Navy will implement a minimum shutdown zone of 50 m 
(164 ft) radius around all pile driving and removal activity. Shutdown 
zones typically include all areas where the underwater SPLs are 
anticipated to equal or exceed the Level A (injury) harassment criteria 
for marine mammals (180-dB isopleth for cetaceans; 190-dB isopleth for 
pinnipeds). In this case, pile driving sounds are expected to attenuate 
below 180 dB at distances of 16 m or less, but the 50-m shutdown is 
intended to further avoid the risk of direct interaction between marine 
mammals and the equipment.
     The buffer zone shall initially be set at a radius of 
2,400 m, which is the width of the Hood Canal at the project site. This 
zone, which would subsume the 160-dB buffer zone, is the maximum area 
that is practicable for the Navy to monitor. The full 120-dB buffer 
zone for vibratory pile driving (modeled as radius of 15,849 m, but 
reduced to 40.3 km\2\ when attenuation due to landmasses is accounted 
for) is so large as to make monitoring impracticable. Additional 
observers will be present in this zone, and any sighted animals would 
be recorded as takes, but it is impossible to guarantee that all 
animals will be observed or to make observations of fine-scale 
behavioral reactions to sound throughout this zone. The 2,400 m (1,644 
ft) zone may be adjusted according to empirical, site-specific data 
after the project begins. Additional buffer zone distances, including 
the 501 m zone for airborne acoustic harassment (harbor seals), and the 
160-dB zone for underwater sound (342 m), may also be adjusted based 
upon the results of hydroacoustic monitoring.
     The shutdown and buffer zones will be monitored throughout 
the time required to drive a pile. If a marine mammal is observed 
entering the buffer zone, a take will be recorded and behaviors 
documented. However, that pile segment will be completed without 
cessation, unless the animal approaches or enters the shutdown zone, at 
which point all pile driving activities will be halted.
     All buffer and shutdown zones will initially be based on 
the distances from the source that are predicted for each threshold 
level. However, in-situ acoustic monitoring will be utilized to 
determine the actual distances to these threshold zones, and the size 
of the shutdown and buffer zones will be adjusted accordingly based on 
received sound pressure levels.
    Monitoring will take place from 30 minutes prior to initiation 
through 30 minutes post-completion of pile driving activities. The 
following additional measures will apply to visual monitoring:
     Monitoring will be conducted by qualified observers. A 
trained observer will be placed from the best vantage point(s) 
practicable to monitor for marine mammals and implement shut-down or 
delay procedures when applicable by calling for the shut-down to the 
hammer operator.
     Prior to the start of pile driving activity, the shutdown 
and safety zones will be monitored for thirty minutes to ensure that 
they are clear of marine mammals. Pile driving will only commence once 
observers have declared the shutdown zone clear of marine mammals; 
animals will be allowed to remain in the buffer zone (i.e., must leave 
of their own volition) and their behavior will be monitored and 
documented.

[[Page 30137]]

     If a marine mammal approaches or enters the shutdown zone 
during the course of pile driving operations, pile driving will be 
halted and delayed until either the animal has voluntarily left and 
been visually confirmed beyond the shutdown zone or thirty minutes have 
passed without re-detection of the animal.
    The following additional measures will be implemented:
     Sound attenuation devices will be utilized during all 
impact pile driving operations.
     The Navy will use soft-start techniques (ramp-up and dry 
fire) recommended by NMFS for impact and vibratory pile driving. The 
soft-start requires contractors to initiate noise from vibratory 
hammers for 15 seconds at reduced energy followed by a 1-minute waiting 
period. This procedure will be repeated two additional times. For 
impact driving, contractors will be required to provide an initial set 
of three strikes from the impact hammer at 40 percent energy, followed 
by a 1-minute waiting period, then two subsequent three strike sets. No 
soft-start procedures exist for pneumatic chipping hammers.
     Pile driving will only be conducted during daylight hours.
     For in-water heavy machinery work other than pile driving 
(if any), if a marine mammal comes within 50 m (164 ft), operations 
shall cease and vessels shall reduce speed to the minimum level 
required to maintain steerage and safe working conditions.
    NMFS has carefully evaluated the mitigation measures described 
previously and considered their effectiveness in past implementation to 
determine whether they are likely to effect the least practicable 
adverse impact on the affected marine mammal species and stocks and 
their habitat. Our evaluation of potential measures includes 
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; (3) the practicability 
of the measure for applicant implementation, including consideration of 
personnel safety, and practicality of implementation.
    It is unlikely that injury, serious injury, or mortality to marine 
mammals would result from any actions undertaken during the pile 
replacement project. The impacts of the project will likely be limited 
to temporary behavioral disturbance. However, to reduce the amount and 
degree of behavioral disturbance that occurs, NMFS and the Navy have 
developed the previously described mitigation measures. These are 
designed to limit the numbers of marine mammals that are exposed to 
underwater sound, by reducing the intensity of sound entering the 
environment, limiting the amount of impact pile driving, and limiting 
the duration of all driving, and to prevent any individual from being 
exposed to levels of sound that could result in injury. Based upon 
experience from previous pile driving projects and the analysis 
contained in NMFS' notice of proposed IHA and in this document, NMFS 
has determined that these mitigation measures provide the means of 
effecting the least practicable adverse impacts on marine mammal 
species or stocks and their habitat.

Monitoring and Reporting

    In order to issue an ITA for an activity, section 101(a)(5)(D) of 
the MMPA states that NMFS must set forth ``requirements pertaining to 
the monitoring and reporting of such taking.'' The MMPA implementing 
regulations at 50 CFR 216.104 (a)(13) indicate that requests for IHAs 
must include the suggested means of accomplishing the necessary 
monitoring and reporting that will result in increased knowledge of the 
species and of the level of taking or impacts on populations of marine 
mammals that are expected to be present.
    The Navy will conduct acoustic monitoring for impact driving of 
steel piles in order to determine the actual distances to the 190-, 
180-, and 160-dB (re 1 [mu]Pa rms) isopleths and to determine the 
relative effectiveness of the bubble curtain system at attenuating 
noise underwater. The Navy will also conduct acoustic monitoring for 
vibratory pile driving in order to determine the actual distance to the 
120-dB isopleth for behavioral harassment relative to background 
levels. Acoustic monitoring will occur for each type of pile 
installation and removal methodology, including impact and vibratory 
pile driving and pneumatic chipping. The Navy's hydroacoustic 
monitoring plan (see ADDRESSES) addresses collection of data for both 
underwater and airborne sounds from the pile replacement project, and 
is discussed in greater detail in NMFS' notice of proposed IHA (76 FR 
6406; February 4, 2011).
    The Navy will collect sighting data and behavioral responses to 
construction for marine mammal species observed in the region of 
activity during the period of activity. All observers will be trained 
in marine mammal identification and behaviors. NMFS requires that the 
observers have no other construction related tasks while conducting 
monitoring. Details regarding monitoring protocols are available in the 
Navy's marine mammal monitoring plan, and were discussed in greater 
detail in NMFS' notice of proposed IHA (76 FR 6406; February 4, 2011). 
The Navy will note in their behavioral observations whether an animal 
remains in the project area following a Level B taking (which would not 
require cessation of activity). This information will ideally make it 
possible to determine whether individuals are taken (within the same 
day) by one or more types of pile driving (i.e., impact and vibratory). 
NMFS requires that, at a minimum, the following information be 
collected on the sighting forms:
     Date and time that pile driving begins or ends;
     Construction activities occurring during each observation 
period;
     Weather parameters identified in the acoustic monitoring 
(e.g., wind, humidity, temperature);
     Tide state and water currents;
     Visibility;
     Species, numbers, and, if possible, sex and age class of 
marine mammals;
     Marine mammal behavior patterns observed, including 
bearing and direction of travel, and if possible, the correlation to 
sound pressure levels;
     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.
    A draft report would be submitted to NMFS within 45 days of the 
completion of acoustic measurements and marine mammal monitoring. The 
results would be summarized in graphical form and include summary 
statistics and time histories of impact sound values for each pile. A 
final report would be prepared and submitted to NMFS within thirty days 
following receipt of comments on the draft report from NMFS. At a 
minimum, the report shall include:
     Size and type of piles;
     A detailed description of the sound attenuation device, 
including design specifications;
     The impact or vibratory hammer force used to drive and 
extract the piles;
     A description of the monitoring equipment;
     The distance between hydrophone(s) and pile;
     The depth of the hydrophone(s);

[[Page 30138]]

     The depth of water in which the pile was driven;
     The depth into the substrate that the pile was driven;
     The physical characteristics of the bottom substrate into 
which the piles were driven;
     The ranges and means for peak, rms, and SELs for each 
pile;
     The results of the acoustic measurements, including the 
frequency spectrum, peak and rms SPLs, and single-strike and cumulative 
SEL with and without the attenuation system;
     The results of the airborne noise measurements including 
dBA and unweighted levels;
     A description of any observable marine mammal behavior in 
the immediate area and, if possible, the correlation to underwater 
sound levels occurring at that time;
     Results, including the detectability of marine mammals, 
species and numbers observed, sighting rates and distances, behavioral 
reactions within and outside of safety zones; and
     A refined take estimate based on the number of marine 
mammals observed in the safety and buffer zones. This may be reported 
as one or both of the following: a rate of take (number of marine 
mammals per hour), or take based on density (number of individuals 
within the area).

Estimated Take by Incidental Harassment

    NMFS is authorizing the Navy to take harbor seals, California sea 
lions, killer whales, Dall's porpoises, and harbor porpoises, by Level 
B harassment only, incidental to pile driving and removal activities. 
These activities are expected to harass marine mammals present in the 
vicinity of the project site through behavioral disturbance only. 
Estimates of the number of marine mammals that may be harassed by the 
activities is based upon the estimated densities of each species in the 
area, the modeled areas of ensonification to various thresholds, and 
the estimated number of pile driving days. Table 1 details the total 
number of authorized takes. Methodology of take estimation was 
discussed in detail in NMFS' notice of proposed IHA (76 FR 6406; 
February 4, 2011).

                          Table 1--Authorized Numbers of Incidental Marine Mammal Takes
----------------------------------------------------------------------------------------------------------------
                                                            Underwater                 Airborne
                                             ----------------------------------------------------      Total
                                                              Impact     Vibratory    Impact and    (percent of
            Species                Density       Impact    disturbance  disturbance   vibratory      stock or
                                                 injury      threshold   threshold   disturbance    population)
                                               threshold     (160 dB)     (120 dB)    threshold
----------------------------------------------------------------------------------------------------------------
California sea lion...........         0.410            0            5          553            0      558 (0.2)
Harbor seal...................         1.31             0            5        1,761            0    1,766 (12.1)
Killer whale..................         0.038            0            9           49          N/A       58 (18.5)
Dall's porpoise...............         0.043            0            1           70          N/A       71 (0.1)
Harbor porpoise...............         0.011            0            0           35          N/A       35 (0.3)
                               ---------------------------------------------------------------------------------
    Total.....................         0               20        2,468            0        2,488  ..............
----------------------------------------------------------------------------------------------------------------

Negligible Impact and Small Numbers Analysis and Determination

    NMFS has defined ``negligible impact'' in 50 CFR 216.103 as ``* * * 
an impact resulting from the specified activity that cannot be 
reasonably expected to, and is not reasonably likely to, adversely 
affect the species or stock through effects on annual rates of 
recruitment or survival.'' In determining whether or not authorized 
incidental take will have a negligible impact on affected species 
stocks, NMFS considers a number of criteria regarding the impact of the 
proposed action, including the number, nature, intensity, and duration 
of Level B harassment take that may occur. Although the Navy's pile 
driving activities may harass marine mammals occurring in the project 
area, impacts are occurring to small, localized groups of animals for 
short durations or to individual cetaceans that may swim through the 
area. No permanent haul-outs or breeding or pupping areas are located 
within the action area. No mortality or injury is anticipated, nor will 
the action result in long-term impacts such as permanent abandonment of 
haul-outs. No impacts are expected at the population or stock level. No 
pinniped stocks known from the action area are listed as threatened or 
endangered under the ESA or determined to be strategic or depleted 
under the MMPA. The number of animals authorized to be taken for each 
species of pinnipeds can be considered small relative to the population 
size. Please see Table 1 for these numbers.
    Based on the foregoing analysis, behavioral disturbance to marine 
mammals in the Hood Canal will be of low intensity and limited 
duration. To ensure minimal disturbance, the Navy will implement the 
mitigation measures described previously, which NMFS has determined 
will serve as the means for effecting the least practicable adverse 
effect on marine mammals stocks or populations and their habitat. NMFS 
finds that the Navy's pile driving activities will result in the 
incidental take of small numbers of marine mammals, and that the 
authorized number of takes will have no more than a negligible impact 
on the affected species and stocks.

Impact on Availa