# Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Wharf Construction Project

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2011-32549

## Record

- **Collection:** Federal Register
- **Document type:** Notice
- **Published:** December 21, 2011
- **Citation:** 76 FR 79410

## Text

DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XA830
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to a Wharf Construction Project

AGENCY:

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

ACTION:

Notice; proposed incidental harassment authorization; request for comments.

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 wharf construction 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, six species of marine mammals during the specified activity.

DATES:

Comments and information must be received no later than January 20, 2012.

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 20910-3225. The mailbox address for providing email comments is
ITP.Laws@noaa.gov.
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 and will generally be posted to
http://www.nmfs.noaa.gov/pr/permits/incidental.htm
without change. All Personal Identifying Information (
e.g.,
name, address) voluntarily submitted by the commenter may be publicly accessible. Do not submit Confidential Business Information or otherwise sensitive or protected information.

An electronic copy of the application containing a list of the references used in this document may be obtained by writing to the address specified above, telephoning the contact listed below (see
FOR FURTHER INFORMATION CONTACT
), or visiting the Internet at:
http://www.nmfs.noaa.gov/pr/permits/incidental.htm.
Documents cited in this notice may also be viewed, by appointment, during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT:

Ben Laws, Office of Protected Resources, NMFS, (301) 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

NMFS received an application on May 25, 2011 from the Navy for the taking of marine mammals incidental to pile driving and removal in association with a wharf construction project in the Hood Canal at Naval Base Kitsap in Bangor, WA (NBKB). The Navy submitted a revised version of the application on August 11, 2011, and, responsive to discussions with NMFS as well as new information about species in the area, submitted a final version deemed adequate and complete by NMFS on November 3, 2011. The wharf construction project is proposed to occur over multiple years; however, this IHA would cover only the initial year of the project, from July 16, 2012, through July 15, 2013. Pile driving and removal activities would occur only within an approved in-water work window from July 16-February 15. Six species of marine mammals are known from 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, which is present only from fall to late spring (October to mid-April), and the California sea lion, which is only present from late summer to late spring (August to early June). Additionally, while the Southern Resident killer whale (listed as endangered under the Endangered Species Act [ESA]) is resident to the inland waters of Washington and British Columbia, it has not been observed in the Hood Canal in over 15 years and was therefore excluded from further analysis.

NBKB provides berthing and support services for OHIO Class ballistic missile submarines (SSBN), also known as TRIDENT submarines. The Navy proposes to begin construction of the Explosive Handling Wharf #2 (EHW-2) facility at NBKB in order to support future program requirements for TRIDENT submarines berthed at NBKB. The Navy states that construction of EHW-2 is necessary because the existing EHW alone will not be able to support future TRIDENT program requirements. Under the proposed action—which includes only the portion of the project that would be completed under this proposed 1-year IHA—a maximum of 195 pile driving days would occur. All piles would be driven with a vibratory hammer for their initial embedment depths, while select piles

would be impact driven for their final 10-15 ft (3-4.6 m) 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 NMFS-promulgated thresholds for assessing pile driving and removal impacts (NMFS, 2005b, 2009), outlined later in this document. The Navy used recommended spreading loss formulas (the practical spreading loss equation for underwater sounds and the spherical spreading loss equation for airborne sounds) and empirically-measured source levels from other 30-66 in (0.8-1.7 m) diameter pile driving events to estimate potential marine mammal exposures. Predicted exposures are outlined later in this document. The calculations predict that no Level A harassments would occur associated with pile driving or construction activities, and that as many as 18,225 Level B harassments may occur during the wharf construction project from sound produced by pile driving activity.

Description of the Specified Activity

NBKB is located on the Hood Canal approximately twenty miles (32 km) west of Seattle, Washington (see Figures 2-1 through 2-4 in the Navy's application). NBKB provides berthing and support services for OHIO Class ballistic missile submarines (SSBN), also known as TRIDENT submarines. The Navy proposes to begin construction of the EHW-2 facility at NBKB in order to support future program requirements for TRIDENT submarines berthed at NBKB. The Navy states that construction of EHW-2 is necessary because the existing EHW alone will not be able to support future TRIDENT program requirements. 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 operations, as well as vibratory removal of falsework piles, associated with the wharf construction project. The proposed activities that would be authorized by this IHA would occur between July 16, 2012, and July 15, 2013. All in-water construction activities within the Hood Canal are only permitted during July 16-February 15 in order to protect spawning fish populations.

As part of the Navy's sea-based strategic deterrence mission, the Navy Strategic Systems Programs directs research, development, manufacturing, testing, evaluation, and operational support for the TRIDENT Fleet Ballistic Missile program. Development of necessary facilities for handling of explosive materials is part of these duties. The EHW-2 would consist of two components: (1) The wharf proper (or Operations Area), including the warping wharf; and (2) two access trestles. Please see Figures 1-1 and 1-2 of the Navy's application for conceptual and schematic representations of the proposed EHW-2. The Operations Area would include a support building and wharf cover. A warping wharf is a long, narrow wharf extension used to position submarines prior to moving into the Operations Area. The access trestles would allow vehicles to travel between the Operations Area and the shore.

The wharf proper would lie approximately 600 ft (183 m) offshore at water depths of 60-100 ft (18-30 m), and would consist of the main wharf, a warping wharf, and lightning protection towers, all pile-supported. It would include a slip (docking area) for submarines, surrounded on three sides by operational wharf area. The main wharf would include an operations support building providing office and storage space and mechanical/electrical system component housing. Additional facility support at the wharf would include heavy duty cranes suspended from the cover, power utility booms, six large lightning protection towers, and camels (operational platforms that float next to a moored vessel).

The access trestles would connect the wharf to the shore. There would be an entrance trestle and an exit trestle; these would be combined over shallow water to reduce overwater area. The trestles would be pile-supported on 24-in (0.6-m) steel pipe piles driven approximately 30 ft (9 m) into the seafloor. Spacing between bents (rows of piles) would be 25 ft (8 m). Concrete pile caps would be cast in place and would support pre-cast concrete deck sections.

For the entire project, a total of up to 1,250 permanent piles ranging in size between 24-48 in (0.6-1.2 m) in diameter would be driven in-water to construct the wharf, with up to three vibratory rigs and one impact driving rig operating simultaneously. Construction would also involve temporary installation of up to 150 falsework piles used as an aid to guide permanent piles to their proper locations. Falsework piles, which would be removed upon installation of the permanent piles, would likely be steel pipe piles and would be driven and removed using a vibratory driver. It has not been determined exactly what parts or how much of the project would be constructed during the first year; however, a maximum of 195 days of pile driving would occur. The analysis contained herein is based upon the maximum of 195 pile driving days, rather than any specific number of piles driven, and assumes that (1) all marine mammals available to be incidentally taken within the relevant area would be; and (2) individual marine mammals may only be incidentally taken once in a 24-h period—for purposes of authorizing specified numbers of take—regardless of actual number of exposures in that period. Table 1 summarizes the number and nature of piles required for the entire project, rather than what subset of piles may be expected to be driven during the first year of construction proposed for this IHA.

Table 1—Summary of piles required for wharf construction (in total)

Feature
Quantity

Total number of permanent in-water piles
Up to 1,250.

Size and number of main wharf piles

24-in: 140.
36-in (0.9-m): 157.
48-in: 263.

Size and number of warping wharf piles

24-in: 80.
36-in: 190.

Size and number of lightning tower piles

24-in: 40.
36-in: 90.

Size and number of trestle piles

24-in: 57.
36-in: 233.

Falsework piles
Up to 150, 18- to 24-in.

Maximum pile driving duration
195 days (under 1-year IHA).

Pile installation would utilize vibratory pile drivers to the greatest extent possible, and the Navy anticipates that most piles would be able to be vibratory driven to within several feet of the required depth. Pile drivability is, to a large degree, a function of soil conditions and the type of pile hammer. The soil conditions encountered during geotechnical explorations at NBKB indicate existing conditions generally consist of fill or sediment of very dense glacially overridden soils. Recent experience at two other construction locations along the NBKB waterfront indicates that most piles should be able to be driven with a vibratory hammer to proper embedment depth. However, difficulties during pile driving may be encountered as a result of obstructions that may exist throughout the project area. Such obstructions may consist of rocks or boulders within the glacially overridden soils. If difficult driving conditions

occur, increased usage of an impact hammer would occur.

Unless difficult driving conditions are encountered, an impact hammer will only be used to proof the load-bearing capacity of approximately every fourth or fifth pile. The industry standard is to proof every pile with an impact hammer; however, in an effort to reduce blow counts from the impact hammer, the engineer of record has agreed to only proof every fourth or fifth pile. A maximum of 200 strikes would be required to proof each pile. Pile production rates are dependent upon required embedment depths, the potential for encountering difficult driving conditions, and the ability to drive multiple piles without a need to relocate the driving rig. Under best-case scenarios (
i.e.,
shallow piles, driving in optimal conditions, using multiple driving rigs), it may be possible to install enough pilings with the vibratory hammer that proofing may be required for up to five piles in a day. Under this likely scenario, with a single impact hammer used to proof up to five piles per day at 200 strikes per pile, it is estimated that up to a maximum of 1,000 strikes from an impact hammer would be required per day.

If difficult subsurface driving conditions (
i.e.,
cobble/boulder zones) are encountered that cause refusal with the vibratory equipment, it may be necessary to use an impact hammer to drive some piles for the remaining portion of their required depth. The worst-case scenario is that a pile would be driven for its entire length using an impact hammer. Given the uncertainty regarding the types and quantities of boulders or cobbles that may be encountered, and the depth at which they may be encountered, the number of strikes necessary to drive a pile its entire length could be approximately 1,000 to 2,000 strikes per pile. The Navy estimates that a possible worst-case daily scenario would require driving three piles full length (at a worst-case of 2,000 strikes per pile) after the piles have become hung on large boulders early in the installation process, with proofing of an additional two piles (at 200 strikes each) that were able to be installed primarily via vibratory means. This worst-case scenario would therefore result in a maximum of 6,400 strikes per day. All piles driven or struck with an impact hammer would be surrounded by a bubble curtain or other sound attenuation device over the full water column to minimize in-water sound. Up to three vibratory rigs and one impact rig would be used at a time. Pile production rate (number of piles driven per day) is affected by many factors: size, type (vertical vs. angled), and location of piles; weather; number of driver rigs operating; equipment reliability; geotechnical (subsurface) conditions; and work stoppages for security or environmental reasons (such as presence of marine mammals).

Pile driving would typically take place 6 days per week. The allowable season for in-water work, including pile driving, at NBKB is July 16 through February 15, which was established by the Washington Department of Fish and Wildlife in coordination with NMFS and the U.S. Fish and Wildlife Service (USFWS) to protect juvenile salmon. Impact pile driving during the first half of the in-water work window (July 16 to September 15) would only occur between 2 hours after sunrise and 2 hours before sunset to protect breeding marbled murrelets (an ESA-listed bird under the jurisdiction of USFWS). Between September 16 and February 15, construction activities occurring in the water would occur during daylight hours (sunrise to sunset). Other construction (not in-water) may occur between 7 a.m. and 10 p.m., year-round.

The number of construction barges (derrick and material) on site at any one time would vary between two and eight depending on the type of construction taking place. The maximum number of eight barges would likely be present at the beginning of construction, with multiple rigs and their support barges required to complete the work at various areas of the wharf. As pile installation progresses, the area will become congested, limiting the space available to support the pile driving rigs and barges. Also, as sections of the wharf are completed the need for some of the rigs/barges will be reduced. As a result, fewer barges would likely be necessary as the project progresses. Tug boats would tow barges to and from the construction site and position the barges for construction activity. Tug boats would leave the site once these tasks were completed and so would not be on site for extended periods; there would be no more than two tug boats on site at any one time. Up to six smaller skiff-type boats would be on site performing various functions in support of construction and monitoring requirements.

Operation of the EHW-2 would not result in an increase in boat traffic along the NBKB waterfront. Rather, a portion of the ongoing operations and boat traffic at the existing EHW and other facilities within the Waterfront Restricted Area (
e.g.,
Delta Pier and Marginal Wharf) would be diverted to the EHW-2. The EHW-2 may be used as a backup explosives handling facility for TRIDENT submarines currently homeported at NBKB when there are no TRIDENT operations at the existing EHW. The EHW-2 may also provide temporary berthing when no ordnance handling operations are occurring at either wharf. No increase in boat traffic would be required to achieve planned operations. The increase in future operations at the waterfront would only require that boats remain at an EHW longer when in port for maintenance and upgrades. The overall level of traffic and activity along the NBKB waterfront would not increase as a result of operating the EHW-2. Operation of the EHW-2 may require approximately twenty additional military and civilian personnel. The EHW-2 would be staffed 24 hours per day, 7 days per week. Maintenance of the EHW-2 would include routine inspections, repair, and replacement of facility components as required. It would not be necessary to replace piles during the design life of the EHW-2. Fouling organisms would not be removed from piles.

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 (μPa). 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 μPa). 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, 1975). 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 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 2. Details of each of the sources are described in the following text.

Table 2—Representative Sound Levels of Anthropogenic sources

Sound source
Frequency range (Hz)
Underwater sound level (dB re 1 μPa)
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 ft)
Blackwell and Greene, 2002.

Vibratory driving of 72-in (1.8 m) steel pipe pile
10-1,500
180 dB rms at 10 m (33 ft)
Illingworth and Rodkin, 2007.

Impact driving of 36-in steel pipe pile
10-1,500
195 dB rms at 10 m
WSDOT, 2007.

Impact driving of 66-in cast-in-steel-shell pile
10-1,500
195 dB rms at 10 m
Reviewed in Hastings and Popper, 2005.

In-water construction activities associated with the project would include impact pile driving and vibratory pile driving and removal. 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 (Caltrans, 2009). Rise time is slower, reducing the probability and severity of injury (USFWS, 2009), and sound energy is distributed over a greater amount of time (Nedwell and Edwards, 2002; Carlson
et al.,
2001).

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).

In the vicinity of the project area, the average broadband ambient underwater sound levels were measured at 114 dB re 1μPa between 100 Hz and 20 kHz (Slater, 2009). Peak spectral sound from industrial activity was noted below the 300 Hz frequency, with maximum levels of 110 dB re 1μPa noted in the 125 Hz band. In the 300 Hz to 5 kHz range, average levels ranged between 83-99 dB re 1μPa. Wind-driven wave sound dominated the background sound environment at approximately 5 kHz and above, and ambient sound levels flattened above 10 kHz.

Airborne sound levels at NBKB vary based on location but are estimated to average around 65 dBA (A-weighted decibels) in the residential and office park areas, with traffic sound ranging from 60-80 dBA during daytime hours (Cavanaugh and Tocci, 1998). The highest levels of airborne sound are produced along the waterfront and at the ordnance handling areas, where estimated sound levels range from 70-90 dBA and may peak at 99 dBA for short durations. These higher sound levels are produced by a combination of sound sources including heavy trucks, forklifts, cranes, marine vessels, mechanized tools and equipment, and other sound-generating industrial or military activities.

Sound Attenuation Devices

Sound levels can be greatly reduced during impact pile driving using sound attenuation devices. There are several types of sound attenuation devices including bubble curtains, cofferdams, and isolation casings (also called temporary noise attenuation piles [TNAP]), and cushion blocks. Bubble curtains 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 (Caltrans, 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 (Caltrans, 2009).

An isolation casing is a hollow pipe that surrounds the pile, isolating it from the in-water work area. The casing is dewatered before pile driving. This device provides levels of sound attenuation similar to that of bubble curtains (Caltrans, 2009). Sound levels can be reduced by 8 to 14 dB. Cushion blocks consist of materials (
e.g.,
wood, nylon) placed atop piles during impact pile driving activities to reduce source levels. Typically sound reduction can range from 4 to a maximum of 26 dB.

Cofferdams are often used during construction for isolating the in-water work area, but may also be used as a sound attenuation device. Dewatered cofferdams may provide the highest levels of sound reduction of any attenuation device; however, they do not eliminate underwater sound because sound can be transmitted through the substrate (Caltrans, 2009). Cofferdams that are not dewatered provide very limited reduction in sound levels.

Both environmental conditions and the characteristics of the sound attenuation device may influence the effectiveness of the device. According to Caltrans (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.,
WSF, 2009; WSDOT, 2008; USFWS, 2009; Caltrans, 2009). 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 (Caltrans, 2009).

Sound Thresholds

Since 1997, NMFS has used generic sound exposure thresholds to determine when an activity in the ocean that produces sound might result in impacts to a marine mammal such that a take by harassment might occur (NMFS, 2005b). To date, no studies have been conducted that examine impacts to marine mammals from pile driving sounds from which empirical sound thresholds have been established. Current NMFS practice 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. A practical sound propagation modeling technique was used by the Navy to estimate the range from the pile driving activity to various SPL thresholds in water. This model follows a geometric propagation loss based on the distance from the driven pile, resulting in a 4.5 dB reduction in level for each doubling of distance from the source. In this model, the SPL at some distance away from the source (
e.g.,
driven pile) is governed by a measured source level, minus the transmission loss of the energy as it dissipates with distance. The formula for underwater TL is:

TL = 15 * log
10
(R
1
/R
2
), where

R
1
= the distance of the modeled SPL from the driven pile, and

R
2
= the distance from the driven pile of the initial measurement.

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]). The propagation environment along the NBKB waterfront conforms to neither spherical nor cylindrical spreading; as the receiver moves away from the shoreline, the water increases in depth, resulting in an expected propagation environment that would lie between spherical and cylindrical spreading loss conditions. Since there is no available data regarding propagation loss along the NBKB waterfront, a practical spreading loss model was adopted as the most likely approximation of the sound propagation environment. Hydroacoustic monitoring results from the Navy's Test Pile Project (see 76 FR 38361; July 30, 2011) will be used, when available, to confirm the validity of the practical spreading model for estimating acoustic propagation in the project area. That project concluded on October 31, 2011.

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. A large quantity of literature regarding SPLs recorded from pile driving projects is available for consideration. In order to determine reasonable SPLs and their associated affects on marine mammals that are likely to result from pile driving at NBKB, studies with similar properties to the proposed action were evaluated. Sound levels associated with vibratory pile removal are assumed to be the same as those during vibratory installation (Caltrans, 2007)—which is likely a conservative assumption—and have been taken into consideration in the modeling analysis. Overall, studies which met the following parameters were considered: (1) Pile size and materials: Steel pipe piles (30-72 in diameter); (2) Hammer machinery: Vibratory and impact hammer; and (3) Physical environment: shallow depth (less than 100 ft [30 m]).

Table 3—Underwater SPLs From Monitored Construction Activities Using Impact Hammers

Project and location
Pile size and type
Water depth
Measured SPLs

Eagle Harbor Maintenance Facility, WA
30-in (0.8 m) steel pipe pile
10 m (33 ft)
192 dB re 1 µPa (rms) at 10 m (33 ft).

Friday Harbor Ferry Terminal, WA
30-in steel pipe pile
10 m
196 dB re 1 µPa (rms) at 10 m.

Unknown, CA
36-in steel pipe pile
10 m
193 dB re 1 µPa (rms) at 10 m.

Mukilteo Test Piles, WA
36-in steel pipe pile
7.3 m (24 ft)
195 dB re 1 µPa (rms) at 10 m.

Anacortes Ferry, WA
36-in steel pipe pile
12.8 m (42 ft)
199 dB re 1 µPa (rms) at 10 m.

Carderock Pier, NBKB, WA
42-in steel pipe pile
14-22 m (48-70 ft)
195 dB re 1 µPa (rms) at 10 m.

Russian River, CA
48-in steel pipe pile
2 m (6.6 ft)
195 dB re 1 µPa (rms) at 10 m.

Unknown, CA
60-in cast-in-steel-shell
10 m
195 dB re 1 µPa (rms) at 10 m.

Richmond-San Rafael Bridge, CA
66-in steel pipe pile
4 m (13 ft)
195 dB re 1 µPa (rms) at 10 m.

Sources: WSDOT, 2005, 2008; Caltrans, 2007; Reyff, 2005; JASCO, 2005; Laughlin, 2005; Navy, 2009.

The tables presented here detail representative pile driving SPLs that have been recorded from similar construction activities in recent years. Due to the similarity of these actions and the Navy's proposed action, these values represent reasonable SPLs which could be anticipated, and which were used in the acoustic modeling and analysis. Table 3 represents SPLs that may be expected during pile installation using an impact hammer. Table 4 represents SPLs that may be expected during pile installation using a vibratory hammer.

Table 4—Underwater SPLs From Monitored Construction Activities Using Vibratory Hammers

Project and location
Pile size and type
Water depth
Measured SPLs

Keystone Ferry Terminal, WA
1

30-in (0.8 m) steel pipe pile
5 m (15 ft)
164 dB re 1 μPa (rms) at 10 m (33 ft).

Keystone Ferry Terminal, WA
1

30-in steel pipe pile
8 m (28 ft)
165 dB re 1 μPa (rms) at 10 m.

Vashon Ferry Terminal, WA
2

30-in steel pipe pile
6 m (20 ft)
165 dB re 1 μPa (rms) at 10 m.

Unknown, CA
36-in steel pipe pile
5 m
170 dB re 1 μPa (rms) at 10 m.

Unknown, CA
36-in steel pipe pile
5 m
175 dB re 1 μPa (rms) at 10 m.

Unknown, CA
72-in steel pipe pile
5 m
170 dB re 1 μPa (rms) at 10 m.

Unknown, CA
72-in steel pipe pile
5 m
180 dB re 1 μPa (rms) at 10 m.

Sources: Laughlin, 2010a; Laughlin, 2010b; Caltrans, 2007.

As described previously in this document, sound attenuation measures, including bubble curtains, can be employed during impact pile driving to reduce the high source pressures. For the wharf construction project, the Navy intends to employ sound reduction techniques during impact pile driving, including the use of sound attenuation systems (
e.g.,
bubble curtain). See “Proposed Mitigation”, later in this document, for more details on the impact reduction and mitigation measures proposed. The calculations of the distances to the marine mammal sound thresholds were calculated for impact installation with the assumption of a 10 dB reduction in source levels from the use of sound attenuation devices, and the Navy used the mitigated distances for impact pile driving for all analysis in their application. The Navy will analyze data from the Test Pile Program to confirm the level of achieved sound attenuation from use of a bubble curtain or similar device using site-specific conditions.

All calculated distances to and the total area encompassed by the marine mammal sound thresholds are provided in Table 5. The Navy used source values of 185 dB for impact driving (the mean SPL of the values presented in Table 3, less 10 dB of sound attenuation from use of a bubble curtain or similar device) and 180 dB for vibratory driving (the worst-case value from Table 4). The 195 dB mean SPL of values presented in Table 3 was considered appropriate because it matched values from projects where larger-size pile was used and, in addition, matched the value obtained from the Carderock project, which was located at the NBKB waterfront and involved similar pile materials, water depth, and bottom type. The maximum value from Table 4 of 180 dB was deemed appropriate for vibratory driving because no data were available for 48-in and 60-in piles. As a result, the most conservative value was selected. Under likely construction scenarios, up to three vibratory drivers would operate simultaneously with one impact driver. Although radial distance and area associated with the zone ensonified to 160 dB (the behavioral harassment threshold for pulsed sounds, such as those produced by impact driving) are presented in Table 5, this zone would be subsumed by the 120 dB zone produced by vibratory driving. Thus, behavioral harassment of marine mammals associated with impact driving is not considered further here. Since the 160 dB threshold and the 120 dB threshold both indicate behavioral harassment, pile driving effects in the two zones are equivalent. Although such a day is not planned, if only the impact driver was operated on a given day, incidental take on that day would likely be lower because the area ensonified to levels producing Level B harassment would be smaller (although actual take would be determined by the numbers of marine mammals in the area on that day). The use of multiple vibratory rigs at the same time would result in a small additive effect with regard to produced SPLs; however, because the sound field produced by vibratory driving would be truncated by land in the Hood Canal, no increase in actual sound field produced would occur. There would be no overlap in the 190/180-dB sound fields produced by rigs operating simultaneously.

Table 5—Calculated Distance(s) to and Area Encompassed by Underwater Marine Mammal Sound Thresholds During Pile Installation

Threshold
Distance

Area, km
2
(mi
2
)

Impact driving, pinniped injury (190 dB)
4.9 m (16.1 ft)
0.0001

Impact driving, cetacean injury (180 dB)
22 m (72.2 ft)
0.002 (0.0008)

Impact driving, disturbance (160 dB)
2

724 m (2,375 ft)
1.65 (0.64)

Vibratory driving, pinniped injury (190 dB)
2.1 m (6.9 ft)
< 0.0001

Vibratory driving, cetacean injury (180 dB)
10 m (32.8 ft)
0.0003 (0.0001)

Vibratory driving, disturbance (120 dB)

13,800 m (45,276 ft)
3

41.4 (15.98)

1
SPLs used for calculations were: 185 dB for impact and 180 dB for vibratory driving.

2
Area of 160-dB zone presented for reference. Estimated incidental take calculated on basis of larger 120-dB zone.

3
Hood Canal average width at site is 2.4 km (1.5 mi), and is fetch limited from N to S at 20.3 km (12.6 mi). Calculated range (over 222 km) is greater than actual sound propagation through Hood Canal due to intervening land masses. 13.8 km (8.6 mi) is the greatest line-of-sight distance from pile driving locations unimpeded by land masses, which would block further propagation of sound.

Hood Canal does not represent open water, or free field, conditions. Therefore, sounds would attenuate as they encounter land masses or bends in the canal. As a result, the calculated distance and areas of impact for the 120 dB threshold cannot actually be attained at the project area. See Figure 6-1 of the Navy's application for a depiction of the size of areas in which each underwater sound threshold is predicted to occur at the project area due to pile driving.

Airborne Sound Propagation Formula
—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. The appropriate airborne sound threshold for behavioral disturbance for all pinnipeds, except harbor seals, is 100 dB re 20 µPa rms (unweighted). For harbor seals, the threshold is 90 dB re 20 µPa rms (unweighted). A spherical spreading loss model, assuming average atmospheric conditions, was used to estimate the distance to the 100 dB and 90 dB re 20 µPa rms (unweighted) airborne thresholds. The formula for calculating spherical spreading loss is:

TL = 20log(R
1
/R
2
)

TL = Transmission loss

R
1
= the distance of the modeled SPL from the driven pile, and

R
2
= the distance from the driven pile of the initial measurement.

Airborne Sound From Pile Installation
—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. In order to determine reasonable airborne SPLs and their associated effects on marine mammals that are likely to result from pile driving at NBKB, studies with similar properties to the proposed action, as described previously, were evaluated. Table 6 details representative pile driving activities that have occurred in recent years. Due to the similarity of these actions and the Navy's proposed action, they represent reasonable SPLs which could be anticipated.

Table 6—Airborne SPLs From Similar Construction Activities

Project & location
Pile size &type
Method
Water depth
Measured SPLs

Northstar Island, AK
1

42-in (1.1 m) steel pipe pile
Impact
Approximately 12 m (40 ft)
97 dB re 20 µPa (rms) at 160 m (525 ft).

Keystone Ferry Terminal, WA
3

30-in (0.8 m) steel pipe pile
Vibratory
Approximately 9 m (30 ft)
97 dB re 20 µPa (rms) at 13 m (40 ft).

Sources: Blackwell
et al.,
2004; Laughlin, 2010b.

Based on in-situ recordings from similar construction activities, the maximum airborne sound levels that would result from impact and vibratory pile driving are estimated to be 97 dB rms re 20 μPa at 160 m and 97 dB rms re 20 μPa at 13 m, respectively (Blackwell
et al.,
2004; Laughlin, 2010b). The distances to the airborne thresholds were calculated with the airborne transmission loss formula presented previously. The Navy has analyzed the combined sound field produced under the multi-rig scenario and calculated the radial distances to the 90 and 100 dB airborne thresholds as 361 m (1,184 ft) and 114 m (374 ft), respectively, equating to areas of 0.41 km
2
(0.16 mi
2
) and 0.04 km
2
(0.02 mi
2
), respectively. These distances would be significantly less for the vibratory driver alone, approximately 28 m (92 ft) and 9 m (30 ft), respectively.

All airborne distances are less than those calculated for underwater sound thresholds. 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. Construction sound associated with the project would not extend beyond the buffer zone for underwater sound that would be established to protect pinnipeds. No haul-outs or rookeries are located within the airborne harassment radii. See Figure 6-2 of the Navy's application for a depiction of the size of areas in which each airborne sound threshold is predicted to occur at the project area due to pile driving.

Description of Marine Mammals in the Area of the Specified Activity

There are six marine mammal species, three cetaceans and three pinnipeds, which may inhabit or transit through the waters nearby NBKB in the Hood Canal. These include the transient killer whale, harbor porpoise, Dall's porpoise, Steller sea lion, California sea lion, and the harbor seal. While the Southern Resident killer whale is resident to the inland waters of Washington and British Columbia, it has not been observed in the Hood Canal in over 15 years, and therefore was excluded from further analysis. The Steller sea lion is the only marine mammal that occurs within the Hood Canal which is listed under the ESA; the Eastern DPS is listed as threatened. All marine mammal species are protected under the MMPA. This section summarizes the population status and abundance of these species, followed by detailed life history information. Table 7 lists the marine mammal species that occur in the vicinity of NBKB and their estimated densities within the project area during the proposed timeframe. Daily maximum abundance data only is presented for sea lions because sightings data have no defined survey area.

Table 7—Marine Mammals Present in the Hood Canal in the Vicinity of NBKB

Species

Stock abundance
1

Relative occurrence in Hood Canal
Season of occurrence

Density during in-water work season
3

(individuals/km
2
)

Steller sea lion

Eastern U.S.DPS

58,334-72,223
2

Occasional presence
Fall to late spring (Oct to mid-April)

3
1.2

California sea lion

U.S. Stock
238,000
Common
Fall to late spring (Aug to early June)

3
26.2

Harbor seal

WA inland waters stock
14,612 (CV = 0.15)
Common
Year-round; resident species in Hood Canal

4
1.31

Killer whale

West Coast transient stock
354
Rare to occasional presence
Year-round

5
0.038

Dall's porpoise

CA/OR/WA stock
42,000 (CV = 0.33)
Rare to occasional presence
Year-round

6
0.014

Harbor porpoise

WA inland waters stock
10,682 (CV = 0.38)
Possible regular to occasional presence
Year-round

7
0.250

1
NMFS marine mammal stock assessment reports at:
http://www.nmfs.noaa.gov/pr/sars/species.htm.

2
Range calculated on basis of total pup counts 2006-2009 and extrapolation factors derived from vital rate parameters estimated for an increasing population.

3
Density for sea lions is not calculated due to the lack of a defined survey area for sightings data. Abundance calculated as the average of the maximum number of individuals present during shore-based surveys at NBKB waterfront during the in-water construction season.

4
Jeffries
et al.,
2003; Huber
et al.,
2001.

5
Density calculated as the maximum number of individuals present at a given time during occurrences of killer whales at Hood Canal in 2003 and 2005 (London 2006) divided by the area of Hood Canal.

6
Density calculated from number of individuals observed in 18 vessel-based surveys of NBKB waterfront area (Tannenbaum
et al.,
2009, 2011).

7
Density calculated from number of individuals observed during vessel-based surveys conducted during Test Pile Program and corrected for detectability (Navy, in prep.).

Steller Sea Lion

Species Description
—Steller sea lions are the largest members of the Otariid (eared seal) family. Steller sea lions show marked sexual dimorphism, in which adult males are noticeably larger and have distinct coloration patterns from females. Males average approximately 1,500 lb (680 kg) and 10 ft (3 m) in length; females average about 700 lb (318 kg) and 8 ft (2.4 m) in length. Adult females have a tawny to silver-colored pelt. Males are characterized by dark, dense fur around their necks, giving a mane-like appearance, and light tawny coloring over the rest of their body (NMFS, 2008a). Steller sea lions are distributed mainly around the coasts to the outer continental shelf along the North Pacific Ocean rim from northern Hokkaido, Japan through the Kuril Islands and Okhotsk Sea, Aleutian Islands and central Bering Sea, southern coast of Alaska and south to California. The population is divided into the Western and the Eastern Distinct Population Segments (DPSs) at 144°W (Cape Suckling, Alaska). The Western DPS includes Steller sea lions that reside in the central and western Gulf of Alaska, Aleutian Islands, as well as those that inhabit coastal waters and breed in Asia (
e.g.,
Japan and Russia). The Eastern DPS extends from California to Alaska, including the Gulf of Alaska.

Status
—Steller sea lions were listed as threatened range-wide under the ESA in 1990. After division into two stocks, the western stock was listed as endangered under the ESA in 1997 and the eastern stock remained classified as threatened. Animals found in the project area are from the eastern stock (NMFS, 1997a; Loughlin, 2002; Angliss and Outlaw, 2005). The eastern stock breeds in rookeries located in southeast Alaska, British Columbia, Oregon, and California; there are no rookeries located in Washington. A final revised species recovery plan addresses both stocks (NMFS, 2008a).

Critical habitat was designated for Steller sea lions in 1993. Critical habitat is associated with breeding and haul-out sites in Alaska, California, and Oregon, and includes so-called `aquatic zones' that extend 3,000 ft (0.9 km) seaward in state and federally managed waters from the baseline or basepoint of each major rookery in Oregon and California (NMFS, 2008a). Three major rookery sites in Oregon (Rogue Reef, Pyramid Rock, and Long Brown Rock and Seal Rock on Orford Reef at Cape Blanco) and three rookery sites in California (Ano Nuevo I, Southeast Farallon I, and Sugarloaf Island and Cape Mendocino) are designated critical habitat (NMFS, 1993). There is no designated critical habitat within the project area.

Limiting factors for recovery of Steller sea lions include reduced food availability, possibly resulting from competition with commercial fisheries; incidental take and intentional kills during commercial fish harvests; subsistence take; entanglement in marine debris; disease; pollution; and harassment. The change in food availability, associated with lowered nutritional status of females and consequent reduced juvenile recruitment, may be the primary cause of the decline (60 FR 51968). Declines of this species in the early 1980s were associated with exceedingly low juvenile survivorship, whereas declines in the 1990s were associated with disproportionately low fecundity (Holmes and York, 2003). Steller sea lions are also sensitive to disturbance at rookeries (during pupping and breeding) and haul-out sites.

The abundance of the Eastern DPS of Steller sea lions is increasing throughout the northern portion of its range (Southeast Alaska and British Columbia), and stable or increasing slowly in the central portion (Oregon through central California). In the southern end of its range (Channel Islands in southern California), it has declined significantly since the late 1930s, and several rookeries and haul-outs have been abandoned. Changes in ocean conditions (
e.g.,
warmer temperatures) may be contributing to habitat changes that favor California sea lions over Steller sea lions in the southern portion of the Steller's range (NMFS, 2007).

The eastern stock was estimated by NMFS in the Recovery Plan for the Steller Sea Lion to number between 45,000 to 51,000 animals (NMFS, 2008a). This stock has been increasing approximately three percent per year over the entire range since the late 1970s (NMFS, 2008a; Pitcher
et al.,
2007). The most recent population estimate for the eastern stock is a minimum of 52,847 individuals; this estimate is not corrected for animals at sea. Actual population is estimated to be within the range 58,334 to 72,223 (Allen and Angliss, 2010). The most recent minimum count for Steller sea lions in Oregon and Washington was 5,813 in 2002 (Pitcher
et al.,
2007; Allen and Angliss, 2010).

The eastern U.S. stock of Steller sea lion is currently listed as threatened under the ESA, and is therefore designated as depleted and classified as a strategic stock under the MMPA. However, the eastern stock of Steller sea lions has been considered a potential candidate for removal from listing under the ESA by the Steller sea lion recovery team and NMFS (NMFS, 2008), based on its annual rate of increase of approximately three percent since the mid-1970s. Although the stock size has increased, the status of this stock relative to its Optimum Sustainable Population (OSP) size is unknown. The overall annual rate of increase of 3.1 percent throughout most of the range (Oregon to southeastern Alaska) of the eastern stock has been consistent and long-term, and may indicate that this stock is reaching OSP size (Pitcher
et al.,
2007).

Behavior and Ecology
—Steller sea lions forage near shore and in pelagic waters. They are capable of traveling long distances in a season and can dive to approximately 1,300 ft (400 m) in depth. They also use terrestrial habitat as haul-out sites for periods of rest, molting, and as rookeries for mating and pupping during the breeding season. At sea, they are often seen alone or in small groups, but may gather in large rafts at the surface near rookeries and haul-outs. Steller sea lions prefer the colder temperate to sub-arctic waters of the North Pacific Ocean. Haul-outs and rookeries usually consist of beaches (gravel, rocky or sand), ledges, and rocky reefs. In the Bering and Okhotsk Seas, sea lions may also haul-out on sea ice, but this is considered atypical behavior (NOAA, 2010a).

Steller sea lions are gregarious animals that often travel or haul out in large groups of up to 45 individuals (Keple, 2002). At sea, groups usually consist of female and subadult males; adult males are usually solitary while at sea (Loughlin, 2002). In the Pacific Northwest, breeding rookeries are located in British Columbia, Oregon, and northern California. Steller sea lions form large rookeries during late spring when adult males arrive and establish territories (Pitcher and Calkins, 1981). Large males aggressively defend territories while non-breeding males remain at peripheral sites or haul-outs. Females arrive soon after and give birth. Most births occur from mid-May through mid-July, and breeding takes

place shortly thereafter. Most pups are weaned within a year. Non-breeding individuals may not return to rookeries during the breeding season but remain at other coastal haul-outs (Scordino, 2006).

Steller sea lions are opportunistic predators, feeding primarily on fish and cephalopods, and their diet varies geographically and seasonally (Bigg, 1985; Merrick
et al.,
1997; Bredesen
et al.,
2006; Guenette
et al.,
2006). Foraging habitat is primarily shallow, nearshore and continental shelf waters; freshwater rivers; and also deep waters (Reeves
et al.,
2008; Scordino, 2010). Steller sea lions occupy major winter haul-out sites on the coast of Vancouver Island in the Strait of Juan de Fuca and the Georgia Basin (Bigg, 1985; Olesiuk, 2008); the closest breeding rookery to the project area is at Carmanah Point near the western entrance to the Strait of Juan de Fuca. There are no known breeding rookeries in Washington (NMFS, 1992; Angliss and Outlaw, 2005) but Eastern stock Steller sea lions are present year-round along the outer coast of Washington at four major haul-out sites (NMFS, 2008a). Both sexes are present in Washington waters; these animals are likely immature or non-breeding adults from rookeries in other areas (NMFS, 2008a). In Washington, Steller sea lions primarily occur at haul-out sites along the outer coast from the Columbia River to Cape Flattery. In inland waters, Steller sea lions use haul-out sites along the Vancouver Island coastline of the Strait of Juan de Fuca (Jeffries
et al.,
2000; COSEWIC, 2003; Olesiuk, 2008). Numbers vary seasonally in Washington waters with peak numbers present during the fall and winter months (Jeffries
et al.,
2000). The highest breeding season Steller sea lion count at Washington haul-out sites was 847 individuals during the period from 1978 to 2001 (Pitcher
et al.,
2007). Non-breeding season surveys of Washington haul-out sites reported as many as 1,458 individuals between 1980 and 2001 (NMFS, 2008a).

Steller sea lions are occasionally present at the Toliva Shoals haul-out site in south Puget Sound (Jeffries
et al.,
2000) and a rock three miles south of Marrowstone Island (NMFS, 2010). Fifteen Steller sea lions have been observed using this haul-out site. At NBKB, Steller sea lions have been observed hauled out on submarines at Delta Pier on several occasions from 2008 through 2011 during fall through spring months (October to April) (Navy 2010). Other potential haul-out sites may include isolated islands, rocky shorelines, jetties, buoys, rafts, and floats (Jeffries
et al.,
2000). Steller sea lions likely utilize foraging habitats in Hood Canal similar to those of the California sea lion and harbor seal, which include marine nearshore and deeper water habitats.

Acoustics
—Like all pinnipeds, the Steller sea lion is amphibious; while all foraging activity takes place in the water, breeding behavior is carried out on land in coastal rookeries (Mulsow and Reichmuth 2008). On land, territorial male Steller sea lions regularly use loud, relatively low-frequency calls/roars to establish breeding territories (Schusterman
et al.,
1970; Loughlin
et al.,
1987). The calls of females range from 0.03 to 3 kHz, with peak frequencies from 0.15 to 1 kHz; typical duration is 1.0 to 1.5 sec (Campbell
et al.,
2002). Pups also produce bleating sounds. Individually distinct vocalizations exchanged between mothers and pups are thought to be the main modality by which reunion occurs when mothers return to crowded rookeries following foraging at sea (Mulsow and Reichmuth, 2008).

Mulsow and Reichmuth (2008) measured the unmasked airborne hearing sensitivity of one male Steller sea lion. The range of best hearing sensitivity was between 5 and 14 kHz. Maximum sensitivity was found at 10 kHz, where the subject had a mean threshold of 7 dB. The underwater hearing threshold of a male Steller sea lion was significantly different from that of a female. The peak sensitivity range for the male was from 1 to 16 kHz, with maximum sensitivity (77 dB re: 1μPa-m) at 1 kHz. The range of best hearing for the female was from 16 to above 25 kHz, with maximum sensitivity (73 dB re: 1μPa-m) at 25 kHz. However, because of the small number of animals tested, the findings could not be attributed to either individual differences in sensitivity or sexual dimorphism (Kastelein
et al.,
2005).

California Sea Lion

Species Description
—California sea lions are members of the Otariid family (eared seals). The species,
Zalophus californianus,
includes three subspecies:
Z. c. wollebaeki
(in the Galapagos Islands),
Z. c. japonicus
(in Japan, but now thought to be extinct), and
Z. c. californianus
(found from southern Mexico to southwestern Canada; referred to here as the California sea lion) (Carretta
et al.,
2007). The California sea lion is sexually dimorphic. Males may reach 1,000 lb (454 kg) and 8 ft (2.4 m) in length; females grow to 300 lb (136 kg) and 6 ft (1.8 m) in length. Their color ranges from chocolate brown in males to a lighter, golden brown in females. At around five years of age, males develop a bony bump on top of the skull called a sagittal crest. The crest is visible in the dog-like profile of male sea lion heads, and hair around the crest gets lighter with age.

Status
—The U.S. stock of California sea lions is estimated at 238,000 and the minimum population size of this stock is 141,842 individuals (Carretta
et al.,
2007). These numbers are from counts during the 2001 breeding season of animals that were ashore at the four major rookeries in southern California and at haul-out sites north to the Oregon/California border. Sea lions that were at-sea or hauled-out at other locations were not counted (Carretta
et al.,
2007). The stock has likely reached its carrying capacity and, even though current total human-caused mortality is unknown (due to a lack of observer coverage in the California set gillnet fishery that historically has been the largest source of human-caused mortalities), California sea lions are not considered a strategic stock under the MMPA because total human-caused mortality is still likely to be less than the potential biological removal (PBR). An estimated 3,000 to 5,000 California sea lions migrate to waters of Washington and British Columbia during the non-breeding season from September to May (Jeffries
et al.,
2000). Peak numbers of up to 1,000 California sea lions occur in Puget Sound (including Hood Canal) during this time period (Jeffries
et al.,
2000).

Distribution
—The geographic distribution of California sea lions includes a breeding range from Baja California, Mexico to southern California. During the summer, California sea lions breed on islands from the Gulf of California to the Channel Islands and seldom travel more than about 31 mi (50 km) from the islands (Bonnell
et al.,
1983). The primary rookeries are located on the California Channel Islands of San Miguel, San Nicolas, Santa Barbara, and San Clemente (Le Boeuf and Bonnell, 1980; Bonnell and Dailey, 1993). Their distribution shifts to the northwest in fall and to the southeast during winter and spring, probably in response to changes in prey availability (Bonnell and Ford, 1987).

The non-breeding distribution extends from Baja California north to Alaska for males, and encompasses the waters of California and Baja California for females (Reeves
et al.,
2008; Maniscalco
et al.,
2004). In the non-breeding season, an estimated 3,000-5,000 adult and sub-adult males migrate northward along the coast to central and northern California, Oregon,

Washington, and Vancouver Island from September to May (Jeffries
et al.,
2000) and return south the following spring (Mate, 1975; Bonnell
et al.,
1983). Along their migration, they are occasionally sighted hundreds of miles offshore (Jefferson
et al.,
1993). Females and juveniles tend to stay closer to the rookeries (Bonnell
et al.,
1983).

California sea lions are present in Hood Canal during much of the year with the exception of mid-June through August, and occur regularly in the vicinity of the project site, as observed during Navy waterfront surveys conducted at NBKB from April 2008 through June 2010 (Navy, 2010). They are known to utilize man-made structures such as piers, jetties, offshore buoys, log booms, and oil platforms (Riedman, 1990), and are often seen rafted off of river mouths (Jeffries
et al.,
2000). 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 58 California sea lions have been observed hauled out together at NBKB (Agness and Tannenbaum, 2009a; Tannenbaum
et al.,
2009a; Walters, 2009). California sea lions have also been observed swimming in the Hood Canal in the vicinity of the project area on several occasions and likely forage in both nearshore marine and inland marine deeper waters (DoN, 2001a).

Behavior and Ecology
—California sea lions feed on a wide variety of prey, including many species of fish and squid (Everitt
et al.,
1981; Roffe and Mate, 1984; Antonelis
et al.,
1990; Lowry
et al.,
1991). In the Puget Sound region, they feed primarily on fish such as Pacific hake (
Merluccius productus
), walleye pollock (
Theragra chalcogramma
), Pacific herring (
Clupea pallasii
), and spiny dogfish (
Squalus acanthias
) (Calambokidis and Baird, 1994). In some locations where salmon runs exist, California sea lions also feed on returning adult and out-migrating juvenile salmonids (London, 2006). Sexual maturity occurs at around four to five years of age for California sea lions (Heath, 2002). California sea lions are gregarious during the breeding season and social on land during other times.

Acoustics
—On land, California sea lions make incessant, raucous barking sounds; these have most of their energy at less than 2 kHz (Schusterman
et al.,
1967). Males vary both the number and rhythm of their barks depending on the social context; the barks appear to control the movements and other behavior patterns of nearby conspecifics (Schusterman, 1977). Females produce barks, squeals, belches, and growls in the frequency range of 0.25-5 kHz, while pups make bleating sounds at 0.25-6 kHz. California sea lions produce two types of underwater sounds: clicks (or short-duration sound pulses) and barks (Schusterman
et al.,
1966, 1967; Schusterman and Baillet, 1969). All underwater sounds have most of their energy below 4 kHz (Schusterman
et al.,
1967).

The range of maximal hearing sensitivity underwater is between 1-28 kHz (Schusterman
et al.,
1972). Functional underwater high frequency hearing limits are between 35-40 kHz, with peak sensitivities from 15-30 kHz (Schusterman
et al.,
1972). The California sea lion shows relatively poor hearing at frequencies below 1 kHz (Kastak and Schusterman, 1998). Peak hearing sensitivities in air are shifted to lower frequencies; the effective upper hearing limit is approximately 36 kHz (Schusterman, 1974). The best range of sound detection is from 2-16 kHz (Schusterman, 1974). Kastak and Schusterman (2002) determined that hearing sensitivity generally worsens with depth—hearing thresholds were lower in shallow water, except at the highest frequency tested (35 kHz), where this trend was reversed. Octave band sound levels of 65-70 dB above the animal's threshold produced an average temporary threshold shift (TTS; discussed later in “Potential Effects of the Specified Activity on Marine Mammals”) of 4.9 dB in the California sea lion (Kastak
et al.,
1999).

Harbor Seal

Species Description
—Harbor seals, which are members of the Phocid family (true seals), inhabit coastal and estuarine waters and shoreline areas from Baja California, Mexico to western Alaska. For management purposes, differences in mean pupping date (
i.e.,
birthing) (Temte, 1986), movement patterns (Jeffries, 1985; Brown, 1988), pollutant loads (Calambokidis
et al.,
1985) and fishery interactions have led to the recognition of three separate harbor seal stocks along the west coast of the continental U.S. (Boveng, 1988). The three distinct stocks are: (1) Inland waters of Washington (including Hood Canal, Puget Sound, and the Strait of Juan de Fuca out to Cape Flattery), (2) outer coast of Oregon and Washington, and (3) California (Carretta
et al.,
2007). The inland waters of Washington stock is the only stock that is expected to occur within the project area.

The average weight for adult seals is about 180 lb (82 kg) and males are slightly larger than females. Male harbor seals weigh up to 245 lb (111 kg) and measure approximately 5 ft (1.5 m) in length. The basic color of harbor seals' coat is gray and mottled but highly variable, from dark with light color rings or spots to light with dark markings (NMFS, 2008c).

Status
—Estimated population numbers for the inland waters of Washington, including the Hood Canal, Puget Sound, and the Strait of Juan de Fuca out to Cape Flattery, are 14,612 individuals (Carretta
et al.,
2007). The minimum population is 12,844 individuals. The harbor seal is the only species of marine mammal that is consistently abundant and considered resident in the Hood Canal (Jeffries
et al.,
2003). The population of harbor seals in Hood Canal is a closed population, meaning that they do not have much movement outside of Hood Canal (London, 2006). The abundance of harbor seals in Hood canal has stabilized, and the population may have reached its carrying capacity in the mid-1990s with an approximate abundance of 1,000 harbor seals (Jeffries
et al.,
2003).

Harbor seals are not considered to be depleted under the MMPA or listed under the ESA. Human-caused mortality relative to PBR is unknown, but it is considered to be small relative to the stock size. Therefore, the Washington Inland Waters stock of harbor seals is not classified as a strategic stock.

Distribution
—Harbor seals are coastal species, rarely found more than 12 mi (20 km) from shore, and frequently occupy bays, estuaries, and inlets (Baird 2001). Individual seals have been observed several miles upstream in coastal rivers. Ideal harbor seal habitat includes haul-out sites, shelter during the breeding periods, and sufficient food (Bjorge, 2002). Haul-out areas can include intertidal and subtidal rock outcrops, sandbars, sandy beaches, peat banks in salt marshes, and man-made structures such as log booms, docks, and recreational floats (Wilson, 1978; Prescott, 1982; Schneider and Payne, 1983; Gilber and Guldager, 1998; Jeffries
et al.,
2000). Human disturbance can affect haul-out choice (Harris
et al.,
2003).

Harbor seals occur throughout Hood Canal and are seen relatively commonly in the area. They are year-round, non-migratory residents, and pup (
i.e.,
give birth) in Hood Canal. Surveys in the Hood Canal from the mid-1970s to 2000 show a fairly stable population between 600-1,200 seals (Jeffries
et al.,
2003). Harbor seals have been observed swimming in the waters along NBKB in every month of surveys conducted from 2007-2010 (Agness and Tannenbaum,

2009b; Tannenbaum
et al.,
2009b). On the NBKB waterfront, harbor seals have not been observed hauling out in the intertidal zone, but have been observed hauled-out on man-made structures such as the floating security fence, buoys, barges, marine vessels, and logs (Agness and Tannebaum, 2009a; Tannenbaum
et al.,
2009a). The main haul-out locations for harbor seals in Hood Canal are located on river delta and tidal exposed areas at Quilcene, Dosewallips, Duckabush, Hamma Hamma, and Skokomish River mouths (see Figure 4-1 of the Navy's application), with the closest haul-out area to the project area being ten miles (16 km) southwest of NBKB at Dosewallips River mouth, outside the potential area of effect for this project (London, 2006).

Behavior and Ecology
—Harbor seals are typically seen in small groups resting on tidal reefs, boulders, mudflats, man-made structures, and sandbars. Harbor seals are opportunistic feeders that adjust their patterns to take advantage of locally and seasonally abundant prey (Payne and Selzer 1989; Baird 2001; Bjørge 2002). The harbor seal diet consists of fish and invertebrates (Bigg, 1981; Roffe and Mate, 1984; Orr
et al.,
2004). Although harbor seals in the Pacific Northwest are common in inshore and estuarine waters, they primarily feed at sea (Orr
et al.,
2004) during high tide. Researchers have found that they complete both shallow and deep dives during hunting depending on the availability of prey (Tollit
et al.,
1997). Their diet in Puget Sound consists of many of the prey resources that are present in the nearshore and deeper waters of NBKB, including hake, herring and adult and out-migrating juvenile salmonids. Harbor seals in Hood Canal are known to feed on returning adult salmon, including ESA-threatened summer-run chum (
Oncorhynchus keta
). Over a 5-year study of harbor seal predation in the Hood Canal, the average percent escapement of summer-run chum consumed was eight percent (London, 2006).

Harbor seals mate at sea and females give birth during the spring and summer, although the pupping season varies by latitude. In coastal and inland regions of Washington, pups are born from April through January. Pups are generally born earlier in the coastal areas and later in the Puget Sound/Hood Canal region (Calambokidis and Jeffries, 1991; Jeffries
et al.,
2000). Suckling harbor seal pups spend as much as forty percent of their time in the water (Bowen
et al.,
1999).

Acoustics
—In air, harbor seal males produce a variety of low-frequency (less than 4 kHz) vocalizations, including snorts, grunts, and growls. Male harbor seals produce communication sounds in the frequency range of 100-1,000 Hz (Richardson
et al.,
1995). Pups make individually unique calls for mother recognition that contain multiple harmonics with main energy below 0.35 kHz (Bigg, 1981; Thomson and Richardson, 1995). Harbor seals hear nearly as well in air as underwater and had lower thresholds than California sea lions (Kastak and Schusterman, 1998). Kastak and Schusterman (1998) reported airborne low frequency (100 Hz) sound detection thresholds at 65.4 dB re 20 μPa for harbor seals. In air, they hear frequencies from 0.25-30 kHz and are most sensitive from 6-16 kHz (Richardson, 1995; Terhune and Turnbull, 1995; Wolski
et al.,
2003).

Adult males also produce underwater sounds during the breeding season that typically range from 0.25-4 kHz (duration range: 0.1 s to multiple seconds; Hanggi and Schusterman 1994). Hanggi and Schusteman (1994) found that there is individual variation in the dominant frequency range of sounds between different males, and Van Parijs
et al.
(2003) reported oceanic, regional, population, and site-specific variation that could be vocal dialects. In water, they hear frequencies from 1-75 kHz (Southall
et al.,
2007) and can detect sound levels as weak as 60-85 dB re 1 μPa within that band. They are most sensitive at frequencies below 50 kHz; above 60 kHz sensitivity rapidly decreases.

Killer Whale

Species Description
—Killer whales are members of the Delphinid family and are the most widely distributed cetacean species in the world. Killer whales have a distinctive color pattern, with black dorsal and white ventral portions. They also have a conspicuous white patch above and behind the eye and a highly variable gray or white saddle area behind the dorsal fin. The species shows considerable sexual dimorphism. Adult males develop larger pectoral flippers, dorsal fins, tail flukes, and girths than females. Male adult killer whales can reach up to 32 ft (9.8 m) in length and weigh nearly 22,000 lb (10,000 kg); females reach 28 ft (8.5 m) in length and weigh up to 16,500 lb (7,500 kg).

Based on appearance, feeding habits, vocalizations, social structure, and distribution and movement patterns there are three types of populations of killer whales (Wiles, 2004; NMFS, 2005). The three distinct forms or types of killer whales recognized in the North Pacific Ocean are: (1) Resident, (2) Transient, and (3) Offshore. The resident and transient populations have been divided further into different subpopulations based mainly on genetic analyses and distribution; not enough is known about the offshore whales to divide them into subpopulations (Wiles, 2004). Only transient killer whales are known from the project area.

Transient killer whales occur throughout the eastern North Pacific, and have primarily been studied in coastal waters. Their geographical range overlaps that of the resident and offshore killer whales. The dorsal fin of transient whales tends to be more erect (straighter at the tip) than those of resident and offshore whales (Ford and Ellis, 1999; Ford
et al.,
2000). Saddle patch pigmentation of transient killer whales is restricted to two patterns, and never has the large areas of black pigmentation intruding into the white of the saddle patch that is seen in resident and offshore types. Transient type whales are often found in long-term stable social units that tend to be smaller than resident social groups (
e.g.,
fewer than ten whales); these social units do not seem as permanent as matrilines are in resident type whales. Transient killer whales feed nearly exclusively on marine mammals (Ford and Ellis, 1999), whereas resident whales primarily eat fish. Offshore whales are presumed to feed primarily on fish, and have been documented feeding on sharks.

Within the transient type, association data (Ford
et al.,
1994; Ford and Ellis, 1999; Matkin
et al.,
1999), acoustic data (Saulitis, 1993; Ford and Ellis, 1999) and genetic data (Hoelzel
et al.,
1998, 2002; Barrett-Lennard, 2000) confirms that three communities of transient whales exist and represent three discrete populations: (1) Gulf of Alaska, Aleutian Islands, and Bering Sea transients, (2) AT1 transients (Prince William Sound, AK; listed as depleted under the MMPA), and (3) West Coast transients. Among the genetically distinct assemblages of transient killer whales in the northeastern Pacific, only the West Coast transient stock, which occurs from southern California to southeastern Alaska, may occur in the project area.

Status
—The West Coast transient stock is a trans-boundary stock, with minimum counts for the population of transient killer whales coming from various photographic datasets. Combining these counts of cataloged transient whales gives a minimum number of 354 individuals for the West Coast transient stock (Allen and Angliss,

2010). However, the number in Washington waters at any one time is probably fewer than twenty individuals (Wiles, 2004). 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. Population trends and status of this stock relative to its Optimum Sustainable Population (OSP) level are currently unknown.

Distribution
—The geographical range of transient killer whales includes the northeast Pacific, with preference for coastal waters of southern Alaska and British Columbia (Krahn
et al.,
2002). Transient killer whales in the eastern North Pacific spend most of their time along the outer coast, but visit Hood Canal and the Puget Sound in search of harbor seals, sea lions, and other prey. Transient occurrence in inland waters appears to peak during August and September (Morton, 1990; Baird and Dill, 1995; Ford and Ellis, 1999) which is the peak time for harbor seal pupping, weaning, and post-weaning (Baird and Dill, 1995). In 2003 and 2005, small groups of transient killer whales (eleven and six individuals, respectively) visited Hood Canal to feed on harbor seals and remained in the area for significant periods of time (59 and 172 days, respectively) between the months of January and July.

Behavior and Ecology
—Transient killer whales show greater variability in habitat use, with some groups spending most of their time foraging in shallow waters close to shore while others hunt almost entirely in open water (Felleman
et al.,
1991; Baird and Dill, 1995; Matkin and Saulitis, 1997). Transient killer whales feed on marine mammals and some seabirds, but apparently no fish (Morton, 1990; Baird and Dill, 1996; Ford
et al.,
1998; Ford and Ellis, 1999; Ford
et al.,
2005). While present in Hood Canal in 2003 and 2005, transient killer whales preyed on harbor seals in the subtidal zone of the nearshore marine and inland marine deeper water habitats (London, 2006). Other observations of foraging transient killer whales indicate they prefer to forage on pinnipeds in shallow, protected waters (Heimlich-Boran, 1988; Saulitis
et al.,
2000). Transient killer whales travel in small, matrilineal groups, but they typically contain fewer than ten animals and their social organization generally is more flexible than that of resident killer whales (Morton, 1990, Ford and Ellis, 1999). These differences in social organization probably relate to differences in foraging (Baird and Whitehead, 2000). There is no information on the reproductive behavior of killer whales in this area.

Acoustics
—Killer whales produce a wide variety of clicks and whistles, but most of their sounds are pulsed, with frequencies ranging from 0.5-25 kHz (dominant frequency range: 1-6 kHz) (Thomson and Richardson, 1995; Richardson
et al.,
1995). Source levels of echolocation signals range between 195-224 dB re 1 μPa-m peak-to-peak (p-p), dominant frequencies range from 20-60 kHz, with durations of about 0.1 s (Au
et al.,
2004). Source levels associated with social sounds have been calculated to range between 131-168 dB re 1 μPa-m and vary with vocalization type (Veirs, 2004).

Both behavioral and auditory brainstem response techniques indicate killer whales can hear in a frequency range of 1-100 kHz and are most sensitive at 20 kHz. This is one of the lowest maximum-sensitivity frequencies known among toothed whales (Szymanski
et al.,
1999).

Dall's Porpoise

Species Description
—Dall's porpoises are members of the Phocoenid (porpoise) family and are common in the North Pacific Ocean. They can reach a maximum length of just under 8 ft (2.4 m) and weigh up to 480 lb (218 kg). Males are slightly larger and thicker than females, which reach lengths of just under 7 ft (2.1 m) long. The body of Dall's porpoises is a very dark gray or black in coloration with variable contrasting white thoracic panels and white `frosting' on the dorsal fin and tail that distinguish them from other cetacean species. These markings and colorations vary with geographic region and life stage, with adults having more distinct patterns.

Based on NMFS stock assessment reports, Dall's porpoises within the Pacific U.S. Exclusive Economic Zone are divided into two discrete, noncontiguous areas: (1) waters off California, Oregon, and Washington, and (2) Alaskan waters (Carretta
et al.,
2008). Only individuals from the CA/OR/WA stock may occur within the project area.

Status
—The NMFS population estimate, recently updated in 2010 for the CA/OR/WA stock, is 42,000 (CV = 0.33) which is based on vessel line transect surveys by Barlow (2010) and Forney (2007). The minimum population is considered to be 32,106. Additional numbers of Dall's porpoises occur in the inland waters of Washington, but the most recent estimate was obtained in 1996 (900 animals; CV = 0.40; Calambokidis
et al.,
1997) and is not included in the overall estimate of abundance for this stock due to the need for more up-to-date information. Dall's porpoise are not listed as depleted under the MMPA or listed under the ESA. The average annual human-caused mortality is estimated to be less than the PBR, and therefore the stock is not classified as a strategic stock under the MMPA. The status of Dall's porpoises in California, Oregon and Washington relative to OSP is not known, and there are insufficient data to evaluate potential trends in abundance.

Distribution
—The Dall's porpoise is found from northern Baja California, Mexico, north to the northern Bering Sea and south to southern Japan (Jefferson
et al.,
1993). The species is only common between 32-62 °N in the eastern North Pacific (Morejohn, 1979; Houck and Jefferson, 1999). North-south movements in California, Oregon, and Washington have been suggested. Dall's porpoises shift their distribution southward during cooler-water periods (Forney and Barlow, 1998). Norris and Prescott (1961) reported finding Dall's porpoises in southern California waters only in the winter, generally when the water temperature was less than 15 °C (59 °F). Seasonal movements have also been noted off Oregon and Washington, where higher densities of Dall's porpoises were sighted offshore in winter and spring and inshore in summer and fall (Green
et al.,
1992).

In Washington, they are most abundant in offshore waters. They are year-round residents in Washington (Green
et al.,
1992), but their distribution is highly variable between years, likely due to changes in oceanographic conditions (Forney and Barlow, 1998). Dall's porpoises are observed throughout the year in the Puget Sound north of Seattle (Osborne
et al.,
1998) and are seen occasionally in southern Puget Sound. Dall's porpoises may also occasionally occur in Hood Canal (Jeffries 2006, personal communication). Nearshore habitats used by Dall's porpoises could include the marine habitats found in the inland marine waters of the Hood Canal. A Dall's porpoise was observed in the deeper water at NBKB in summer 2008 (Tannenbaum
et al.,
2009a).

Behavior and Ecology
—Dall's porpoises can be opportunistic feeders but primarily consume schooling forage fish. They are known to eat squid, crustaceans, and fishes such as blackbelly eelpout (
Lycodopsis pacifica
), herring, pollock, hake, and Pacific sandlance (
Ammodytes hexapterus
) (Walker
et al.,
1998).

Groups of Dall's porpoises generally include fewer than ten individuals and are fluid, probably aggregating for feeding (Jefferson, 1990, 1991; Houck and Jefferson, 1999). Dall's porpoises become sexually mature at three and a half to eight years of age (Houck and Jefferson, 1999) and give birth to a single calf after ten to twelve months. Breeding and calving typically occurs in the spring and summer (Angell and Balcomb, 1982). In the North Pacific, there is a strong summer calving peak from early June through August (Ferrero and Walker, 1999), and a smaller peak in March (Jefferson, 1989). Resident Dall's porpoises breed in Puget Sound from August to September.

Acoustics
—Only short duration pulsed sounds have been recorded for Dall's porpoises (Houck and Jefferson, 1999); this species apparently does not whistle often (Richardson
et al.,
1995). Dall's porpoises produce short duration (50-1,500 μs), high-frequency, narrow band clicks, with peak energies between 120-160 kHz (Jefferson, 1988). There is no published data on the hearing abilities of this species.

Harbor Porpoise

Species Description
—Harbor porpoises belong to the Phocoenid (porpoise) family and are found extensively along the Pacific U.S. coast. Harbor porpoises are small, with males reaching average lengths of approximately 5 ft (1.5 m); Females are slightly larger with an average length of 5.5 ft (1.7 m). The average adult harbor porpoise weighs between 135-170 lb (61-77 kg). Harbor porpoises have a dark grey coloration on their backs, with their belly and throats white. They have a dark grey chin patch and intermediate shades of grey along their sides.

Recent preliminary genetic analyses of samples ranging from Monterey, CA to Vancouver Island, BC indicate that there is small-scale subdivision within the U.S. portion of this range (Chivers
et al.,
2002). Although geographic structure exists along an almost continuous distribution of harbor porpoises from California to Alaska, stock boundaries are difficult to draw because any rigid line is generally arbitrary from a biological perspective. Nevertheless, based on genetic data and density discontinuities identified from aerial surveys, NMFS identifies eight stocks in the Northeast Pacific Ocean. Pacific coast harbor porpoise stocks include: (1) Monterey Bay, (2) San Francisco-Russian River, (3) northern California/southern Oregon, (4) Oregon/Washington coastal, (5) inland Washington, (6) Southeast Alaska, (7) Gulf of Alaska, and (8) Bering Sea. Only individuals from the Washington Inland Waters stock may occur in the project area.

Status
—Aerial surveys of the inland waters of Washington and southern British Columbia were conducted during August of 2002 and 2003 (J. Laake, unpubl. data). These aerial surveys included the Strait of Juan de Fuca, San Juan Islands, Gulf Islands, and Strait of Georgia, which includes waters inhabited by the Washington Inland Waters stock of harbor porpoises as well as harbor porpoises from British Columbia. An average of the 2002 and 2003 estimates of abundance in U.S. waters resulted in an uncorrected abundance of 3,123 (CV= 0.10) harbor porpoises in Washington inland waters (J. Laake, unpubl. data). When corrected for availability and perception bias, the estimated abundance for the Washington Inland Waters stock of harbor porpoise is 10,682 (CV = 0.38) animals (Carretta
et al.,
2008). The minimum population estimate is 7,841. Harbor porpoise are not listed as depleted under the MMPA or listed under the ESA. Based on currently available data, the total level of human-caused mortality is not known to exceed the PBR. Therefore, the Washington Inland Waters harbor porpoise stock is not classified as strategic. The status of this stock relative to its OSP level and population trends is unknown. Although long-term harbor porpoise sightings in southern Puget Sound have declined since the 1940s, sightings have increased in Puget Sound and northern Hood Canal in recent years and are now considered to regularly occur year-round in these waters (Calambokidis 2010, pers. comm). This 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).

Distribution
—Harbor porpoises are generally found in cool temperate to subarctic waters over the continental shelf in both the North Atlantic and North Pacific (Read 1999). This species is seldom found in waters warmer than 17 °C (63 °F; Read 1999) or south of Point Conception (Hubbs 1960; Barlow and Hanan 1995). Harbor porpoises can be found year-round primarily in the shallow coastal waters of harbors, bays, and river mouths (Green
et al.,
1992). Along the Pacific coast, harbor porpoises occur from Monterey Bay, California to the Aleutian Islands and west to Japan (Reeves
et al.,
2002). Harbor porpoises are known to occur in Puget Sound year round (Osmek
et al.,
1996, 1998; Carretta
et al.,
2007), and harbor porpoise observations in northern Hood Canal have increased in recent years (Calambokidis 2010, pers. comm.). Prior to recent construction projects conducted by the Navy at NBKB, harbor porpoises were considered as likely occurring only occasionally in the project area. A single harbor porpoise had been sighted in deeper water at NBKB during 2010 field observations (SAIC, 2010). 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. Following these sightings, the Navy conducted dedicated line transect surveys, recording multiple additional sightings of harbor porpoise, and have revised local density estimates accordingly. The current density estimates are based upon a small sample size of transect surveys, and may be further revised as more information becomes available from ongoing Navy survey efforts.

Behavior and Ecology
—Harbor porpoises are non-social animals usually seen in small groups of two to five animals. Little is known about their social behavior. Harbor porpoises can be opportunistic foragers but primarily consume schooling forage fish (Osmek
et al.,
1996; Bowen and Siniff, 1999; Reeves
et al.,
2002). Along the coast of Washington, harbor porpoises primarily feed on herring, market squid (
Loligo opalescens
) and eulachon (
Thaleichthys pacificus
) (Gearin
et al.,
1994). Females reach sexual maturity at three to four years of age and may give birth every year for several years in a row. Calves are born in late spring (Read, 1990; Read and Hohn, 1995). Dall's and harbor porpoises appear to hybridize relatively frequently in the Puget Sound area (Willis
et al.,
2004).

Acoustics
—Harbor porpoise vocalizations include clicks and pulses (Ketten, 1998), as well as whistle-like signals (Verboom and Kastelein 1995). The dominant frequency range is 110-150 kHz, with source levels of 135-177 dB re 1 μPa-m (Ketten 1998). Echolocation signals include one or two low-frequency components in the 1.4-2.5 kHz range (Verboom and Kastelein 1995).

A behavioral audiogram of a harbor porpoise indicated the range of best sensitivity is 8-32 kHz at levels between 45-50 dB re 1 μPa-m (Andersen 1970); however, auditory-evoked potential studies showed a much higher frequency of approximately 125-130 kHz (Bibikov 1992). The auditory-evoked potential method suggests that the harbor porpoise actually has two frequency ranges of best sensitivity. More recent psycho-acoustic studies

found the range of best hearing to be 16-140 kHz, with a reduced sensitivity around 64 kHz (Kastelein
et al.,
2002). Maximum sensitivity occurs between 100-140 kHz (Kastelein
et al.,
2002).

Potential Effects of the Specified Activity on Marine Mammals

NMFS has determined that pile driving, as outlined in the project description, has the potential to result in behavioral harassment of Steller sea lions, California sea lions, harbor seals, harbor porpoises, Dall's porpoises, and killer whales that may be swimming, foraging, or resting in the project vicinity while pile driving is being conducted. Pile driving could potentially harass those pinnipeds that are in the water close to the project site, whether their heads are above or below the surface.

Marine Mammal Hearing

The primary effect on marine mammals anticipated from the specified activities 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.

As mentioned previously in this document, three pinniped and three cetacean species are likely to occur in the proposed project area. Of the three cetacean species likely to occur in the project area, two are classified as high frequency cetaceans (Dall's and harbor porpoises) and one is classified as a mid-frequency cetacean (killer whales) (Southall
et al.,
2007).

Underwater 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; O'Keefe and Young, 1984; DoN, 2001b).

Hearing Impairment and Other Physical Effects
—Marine mammals exposed to high intensity sound repeatedly or for prolonged periods can experience hearing threshold shift (TS), which is the loss of hearing sensitivity at certain frequency ranges (Kastak
et al.,
1999; Schlundt
et al.,
2000; Finneran
et al.,
2002, 2005). TS can be permanent (PTS), in which case the loss of hearing sensitivity is not recoverable, or temporary (TTS), in which case the animal's hearing threshold 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, either permanently or temporarily. However, this depends on both the frequency and duration of TTS, as well as the biological context in which it occurs. TTS of limited duration, occurring in a frequency range that does not coincide with that used for recognition of important acoustic cues, would have little to no effect on an animal's fitness. Repeated sound exposure that leads to TTS could cause PTS. PTS, in the unlikely event that it occurred, would constitute injury, but TTS is not considered injury (Southall
et al.,
2007). It is unlikely that the project would result in any cases of temporary or especially permanent hearing impairment or any significant non-auditory physical or physiological effects for reasons discussed later in this document. Some behavioral disturbance is expected, but it is likely that this would be localized and short-term because of the short project duration.

Several aspects of the planned monitoring and mitigation measures for this project (see the “Proposed Mitigation” and “Proposed Monitoring and Reporting” sections later in this document) are designed to detect marine mammals occurring near the pile driving to avoid exposing them to sound pulses that might, in theory, cause hearing impairment. In addition, many cetaceans are likely to show some 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 μPa
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 μPa 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 μPa 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 μPa 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 μPa 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 μPa 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 μPa
2
-s (15 dB higher than the TTS threshold for an impulse). Given the higher level of sound necessary to cause PTS as compared with TTS, it is considerably less likely that PTS could occur.

Non-auditory Physiological Effects
—Non-auditory physiological effects or injuries that theoretically might occur in marine mammals exposed to strong underwater sound include stress, neurological effects, bubble formation, resonance effects, and other types of organ or tissue damage (Cox
et al.,
2006; Southall
et al.,
2007). Studies examining such effects are limited. In general, little is known about the potential for pile driving to cause auditory impairment or other physical effects in marine mammals. Available data suggest that such effects, if they occur at all, would presumably be limited to short distances from the sound source and to activities that extend over a prolonged period. The available data do not allow identification of a specific exposure level above which non-auditory effects can be expected (Southall
et al.,
2007) or any meaningful quantitative predictions of the numbers (if any) of marine mammals that might be affected in those ways. Marine mammals that show behavioral avoidance of pile driving, including some odontocetes and some pinnipeds, are especially unlikely to incur auditory impairment or non-auditory physical effects.

Measured source levels from impact pile driving can be as high as 214 dB re 1 μPa 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 μPa, 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 μPa
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.

Disturbance Reactions

Disturbance includes a variety of effects, including subtle changes in behavior, more conspicuous changes in activities, and displacement. Reactions to sound, if any, depend on species, state of maturity, experience, current activity, reproductive state, time of day, and many other factors (Richardson
et al.,
1995; Wartzok
et al.,
2004; Southall
et al.,
2007; Weilgart, 2007). Behavioral responses to sound are highly variable and context specific. For each potential behavioral change, the magnitude of the change ultimately determines the severity of the response. A number of factors may influence an animal's response to sound, including its previous experience, its auditory sensitivity, its biological and social status (including age and sex), and its behavioral state and activity at the time of exposure.

Habituation can occur when an animal's response to a stimulus wanes with repeated exposure, usually in the absence of unpleasant associated events (Wartzok
et al.,
2003/04). Animals are most likely to habituate to sounds that are predictable and unvarying. The opposite process is sensitization, when an unpleasant experience leads to subsequent responses, often in the form of avoidance, at a lower level of exposure. Behavioral state may affect the type of response as well. For example, animals that are resting may show greater behavioral change in response to disturbing 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; Caltrans, 2001, 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 (Caltrans 2001, 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

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2011-32549. Public record. Not legal advice.