Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Replacement of the Elliott Bay Seawall in Seattle, Washington
Proposed Rule; Request For Comments.
NMFS has received a request from the Seattle Department of Transportation (SDOT), on behalf of the City of Seattle (City), for authorization to take marine mammals incidental to construction associated with the replacement of the Elliott Bay Seawall in Seattle, Washington, for the period September 2013 to September 2018. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is proposing regulations to govern that take and requests information, suggestions, and comments on these proposed regulations.
Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Replacement of the Elliott Bay Seawall in Seattle, Washington
3 actions from October 24th, 2012 to September 2013
October 24th, 2012
- Final Action
Table of Contents Back to Top
- FOR FURTHER INFORMATION CONTACT:
- SUPPLEMENTARY INFORMATION:
- Summary of Request
- Description of the Specified Activity
- Dates and Duration of Specified Activity
- Specified Geographical Region
- Brief Background on Sound
- Metrics Used in This Document
- Sound Thresholds
- Distance to Sound Thresholds
- Description of Marine Mammals in the Area of the Specified Activity
- Harbor Seal
- California Sea Lion
- Steller Sea Lions
- Harbor Porpoise
- Dall's Porpoise
- Killer Whale
- Humpback Whale
- Gray Whale
- Potential Effects of the Specified Activity on Marine Mammals
- Hearing Impairment and Other Physiological Effects
- Anticipated Effects on Marine Mammal Habitat
- Impacts to Prey Species
- Proposed Mitigation
- Limited Impact Pile Driving
- Containment of Impact Pile Driving
- Additional Attenuation Measures
- Marine Mammal Exclusion Zones
- Shutdown and Delay Procedures
- Proposed Monitoring and Reporting
- Visual Monitoring
- Acoustic Monitoring
- Adaptive Management
- Estimated Take by Incidental Harassment
- Negligible Impact and Small Numbers Analyses and Preliminary Determination
- Harbor Seal
- California Sea Lion
- Steller Sea Lion
- Harbor Porpoise
- Dall's Porpoise
- Killer Whale
- Gray Whale
- Humpback Whale
- Impact on Availability of Affected Species or Stock for Taking for Subsistence Uses
- Endangered Species Act (ESA)
- National Environmental Policy Act (NEPA)
- Information Solicited
- List of Subjects in 50 CFR Part 217
- PART 217—REGULATIONS GOVERNING THE TAKE OF MARINE MAMMALS INCIDENTAL TO SPECIFIED ACTIVITIES
- Subpart W—Taking and Importing Marine Mammals; Elliott Bay Seawall Project
- Subpart W—Taking of Marine Mammals Incidental to the Elliott Bay Seawall Project
Tables Back to Top
- Table 1—Temporary Containment Wall Installation and Removal
- Table 2—Existing Pile Removal
- Table 3—Permanent Pile Installation
- Table 4—Proposed Project Construction Schedule
- Table 5—Summary of Near-Source (10-m) Unattenuated Sound Pressures for In-Water Pile Installation Using an Impact Hammer and Vibratory Driver/Extractor
- Table 6—Calculated Distances to Threshold Values for Pile-Related Activities
- Table 7—Marine Mammal Species or Distinct Population Segments That Could Occur in the Proposed Project Area
- Table 8—Estimated Marine Mammal Takes for Proposed Authorization
DATES: Back to Top
Comments and information must be received no later than May 13, 2013.
ADDRESSES: Back to Top
You may submit comments on this document, identified by 0648-BC69, by any of the following methods:
- Electronic Submission: Submit all electronic public comments via the Federal e-Rulemaking Portal www.regulations.gov. To submit comments via the e-Rulemaking Portal, first click the Submit a Comment icon, then enter 0648-BC69 in the keyword search. Locate the document you wish to comment on from the resulting list and click on the Submit a Comment icon on the right of that line.
- Hand delivery or mailing of comments via paper or disc should be addressed to P. Michael Payne, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910.
Comments regarding any aspect of the collection of information requirement contained in this proposed rule should be sent to NMFS via one of the means provided here and to the Office of Information and Regulatory Affairs, NEOB-10202, Office of Management and Budget, Attn: Desk Office, Washington, DC 20503, OIRA@omb.eop.gov.
Instructions: Comments must be submitted by one of the above methods to ensure that the comments are received, documented, and considered by NMFS. Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered. All comments received are a part of the public record and will generally be posted for public viewing on www.regulations.gov without change. All personal identifying information (e.g., name, address) submitted voluntarily by the sender will be publicly accessible. Do not submit confidential business information, or otherwise sensitive or protected information. NMFS will accept anonymous comments (enter N/A in the required fields if you wish to remain anonymous). Attachments to electronic comments will be accepted in Microsoft Word, Excel, or Adobe PDF file formats only.
FOR FURTHER INFORMATION CONTACT: Back to Top
Michelle Magliocca, Office of Protected Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION: Back to Top
Availability Back to Top
A copy of SDOT's application, and other supplemental documents, may be obtained by visiting the Internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications. Documents cited in this notice may also be viewed, by appointment, during regular business hours, at the aforementioned address.
Background Back to Top
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.”
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 Back to Top
On September 17, 2012, NMFS received a complete application from SDOT requesting authorization for the take of nine marine mammal species incidental to replacement of the Elliott Bay Seawall in Seattle, Washington, over the course of 5 years. The purpose of the proposed project is to reduce the risks of coastal storm and seismic damage and to protect public safety, critical infrastructure, and associated economic activities in the area. Additionally, the project would improve the degraded ecosystem functions and processes of the Elliott Bay nearshore around the existing seawall. Noise produced during pile installation and removal activities has the potential to take marine mammals. SDOT requested, and NMFS is proposing, authorization to take nine marine mammal species by Level B harassment only: Pacific harbor seal (Phoca vitulina), California sea lion (Zalophus californianus), Steller sea lion (Eumetopias jubatus), harbor porpoise (Phocoena phocoena), Dall's porpoise (Phocoenoides dalli), southern resident and transient killer whales (Orcinus orca), humpback whale (Megaptera novaengliae), and gray whale (Eschrichtius jubatus). Injury or mortality is unlikely during the proposed project, and take by Level A harassment (including injury) or mortality is not requested nor proposed for authorization.
Description of the Specified Activity Back to Top
SDOT proposes to replace the Elliott Bay Seawall from South Washington Street to Broad Street, along the Seattle waterfront abutting Elliott Bay in King County, Washington. The purpose of the project is to reduce the risks of coastal storm and seismic damages and to protect public safety, critical infrastructure, and associated economic activities along Seattle's central waterfront. Additionally, the project would improve nearshore ecosystem functions and processes in the vicinity of the existing seawall. The proposed project would be constructed in two phases: Phase 1 would extend for about 3,600 linear feet (ft) (1 kilometer (km)) from South Washington Street to Virginia Street, and Phase 2 would extend for about 3,500 linear ft (1 km) from Virginia to Broad Streets.
The new seawall would be constructed landward of the existing seawall face and result in a net setback of the wall from its existing location. The majority of seawall construction would occur behind a temporary steel sheet pile containment wall that would be placed waterward of the existing seawall complex and extend the full length of the construction work area during each construction season. The seawall structure would consist of a soil improvement structure that would stabilize the soils behind the existing seawall and may include anchors or tie-backs that extend down to non-liquefiable soil for seismic stability. A four-lane primary arterial that runs along the entire length of the seawall would need to be relocated during seawall construction. A stormwater treatment system would be installed to treat stormwater runoff from the project area using basic treatment technology to meet City code. Public amenities resulting from the project would include replaced railings, restoration of the Washington Street boat landing, riparian planters, street plantings, and reconstructed sidewalks.
Construction activities that may result in the take of marine mammals include in-water vibratory and impact pile installation and removal. An APE 200 or equivalent-type of vibratory hammer would be used, with no more than an APE 400 model required for a worst-case scenario. A Delmag D46-32 or equivalent-type of impact hammer would be used, with no more than a Delmag D62-22 required for a worst-case scenario. A total of 1,930 piles would be installed over a 5-year period, and 1,740 of those piles would also be removed (leaving 190 permanent piles). In addition, 80 existing piles would be removed over a 5-year period. All proposed in-water pile installation and removal is summarized in Tables 1 through 3 below. To account for potential mid-project changes in pile numbers, SDOT included a 10 percent contingency in their estimates for installation and removal. These contingency numbers are used in all calculations and assessments in this document. Roughly the same number and distribution of in-water steel sheet piles and permanent piles is expected for each year of the project. Piles installed in upland areas are not expected to result in the take of marine mammals because sound levels would not reach NMFS threshold criteria underwater and there are no pinniped haul-outs in the immediate area. Upland pile installation is not mentioned further.
Prior to excavation and demolition of the existing seawall, a temporary containment wall constructed of steel sheet piles would be installed in each construction segment (Table 1). The temporary containment wall would be installed by vibratory driving and would be located in the water about 5 ft (1.5 m) waterward of the existing seawall. It would remain in place throughout the duration of construction. After construction, the temporary containment wall would be removed with vibratory equipment. In the rare case where steel sheet piles would be load bearing, an impact hammer may be required to “proof” or set the piles. The temporary containment wall would serve to prevent adverse effects on nearshore marine habitat from the release of turbidity and contaminants associated with seawall excavation and demolition.
|Construction phase||Pile pairs1 (10% contingency included)||Maximum duration (days)||Maximum hours per day||Installation/removal method|
|[Steel sheet piles only]|
|1Steel sheet pile pairs only (48 inches wide).|
|2Number equals 20 percent of estimated number of piles installed per phase.|
|3Total estimated installation time is 8 hours of actual impact driving.|
|4Total estimated installation time is 12 hours of actual impact driving.|
|Phase 1 (Years 1-3)||1,023||60||12||vibratory.|
|Estimated number of piles that would require proofing2||205||34||10||impact.|
|Phase II (Years 4-5)||717||40||12||vibratory.|
|Estimated number of piles that would require proofing2||143||34||10||impact.|
Existing creosote-treated timber piles and concrete piles located waterward of the existing seawall face that would interfere with construction would be removed using a vibratory extraction method (Table 2). Timber pilings that break during extraction would be cut off 2 ft (0.6 m) below the mudline.
|Construction phase||Piles1||Pile type||Justification for removal||Maximum duration (days)||Maximum hours per day||Removal method|
|[Timber and concrete piles only]|
|1Number includes 10 percent contingency.|
|2Assumed to be 14-in diameter.|
|3Assumed to be 18-in diameter.|
|Phase 1 (Excluding Washington Street Boat Landing)||20||Creosote-treated timber2||Currently not used; from previous uses along wall||2||12||vibratory.|
|Phase I (Washington Street Boat Landing Only)||8||Creosote-treated timber2||Support existing pier structure||1||12||vibratory.|
|Phase II||49||Creosote-treated timber2||Currently not used; from previous uses along wall||2||12||vibratory.|
|Phase II||3||Concrete3||Currently not used; from previous uses along wall||1||12||vibratory.|
About 190 permanent concrete piles would be installed on either side of the temporary sheet pile containment wall using impact pile installation (Table 3). All in-water permanent piles are assumed to be 16.5-in-diameter (42-cm) precast concrete octagonal piles. The temporary sheet pile containment wall may serve as an attenuation device during impact pile installation to reduce sound levels by up to 10 decibels (dB). The concrete pilings installed landward of the temporary containment wall are intended to provide permanent structural support for cantilevered sidewalks and pier areas with high vehicle traffic. The remaining pilings installed waterward of the temporary containment wall would support the replacement of the Washington Street Boat Landing.
|Construction phase||Piles||Justification for installation||Maximum duration (days)||Maximum hours per day||Installation method|
|[16.5-in-diameter (42-cm) precast concrete octagonal piles only]|
|Phase I (Excluding Washington Street Boat Landing)||92||To support sidewalk, viewing areas, and vehicular traffic access||11||10||Impact.|
|Phase I (Washington Street Boat Landing Only)||15||To support new pier structure||2||10||Impact.|
|Phase II||83||To support sidewalk and viewing areas||10||10||Impact.|
Dates and Duration of Specified Activity Back to Top
Seawall construction is expected to occur in two phases: Phase 1, which includes the area of the Central Seawall, and Phase 2, which includes the area of the North Seawall (Table 4). Phase 1 includes three construction segments, and Phase 2 includes two construction segments; each segment represents 1 to 2 years of construction. Construction is scheduled to begin with Phase I work in fall 2013. The three segments of Phase 1 would be constructed over three construction seasons with two summer shutdown periods from Memorial Day weekend through Labor Day weekend to accommodate the primary tourist and business season. Phase 2 construction is expected to begin following completion of Phase 1 and would occur over two 2-year construction seasons with a summer shutdown period each year. SDOT's Letter of Authorization (LOA) request covers the construction period from 2013 to 2018, from the start of Phase 1, Segment 1 to the end of Phase 2, Segment 1. A request for another MMPA authorization may be submitted for any further construction.
|*Note: Years 6 and 7 would not be covered under this LOA request because the MMPA limits incidental take authorizations to 5-year periods.|
|1 (Central Seawall)||I||Year 1 (Fall 2013-Spring 2014).|
|II||Year 2 (Fall 2014-Spring 2015).|
|III||Year 3 (Fall 2015-Spring 2016).|
|2 (North Seawall)||I||Years 4 and 5 (Fall 2016-Spring 2018).|
|II||Years 6 and 7 (Fall 2018-Spring 2020).*|
Specified Geographical Region Back to Top
The Elliott Bay Seawall runs along the downtown Seattle waterfront in King County, Washington. SDOT's proposed project would occur between South Washington Street and Broad Street, which abut Elliott Bay, a 21-square kilometer (km  ) urban embayment in central Puget Sound. The inner bay receives fresh water from the Duwamish River and most of the stormwater runoff from 67 km  of highly developed land in metropolitan Seattle. This is an important industrial region and home to the Port of Seattle, which ranked as the nation's sixth busiest U.S. seaport in 2010.
The region of the specified activity (or “area of potential effects,” as described in SDOT's application) is the area in which elevated sound levels from pile-related activities could result in the take of marine mammals. This area includes the proposed construction zone, Elliott Bay, and a portion of Puget Sound. The construction zone extends for about 7,100 linear ft (2,165 m) along the Seattle shoreline and is mostly concentrated in upland areas. The area of in-water pile installation and removal activities would be restricted to the length of the seawall and waterward to within 15 ft (4.6 m) of the seawall face, and to depths less than 30 feet (9.1 m). SDOT calculated unattenuated and unobstructed vibratory pile installation (or removal) to propagate up to 2.5 miles (4 km) from the sound source with high enough sound levels to meet NMFS' acoustic threshold criteria for marine mammal harassment (see Sound Thresholds section below). SDOT expects that pile-related construction noise could extend throughout the nearshore and open water environments to just west of Alki Point and a limited distance into the East Waterway of the Lower Duwamish River (a highly industrialized waterway).
Brief Background on Sound Back to Top
An understanding of the basic properties of underwater sound is necessary to comprehend many of the concepts and analyses presented in this document. A summary is included below.
Sound is a wave of pressure variations propagating through a medium (e.g., water). Pressure variations are created by compressing and relaxing the medium. Sound measurements can be expressed in two forms: intensity and pressure. Acoustic intensity is the average rate of energy transmitted through a unit area in a specified direction and is expressed in watts per square meter (W/m  ). Acoustic intensity is rarely measured directly, but rather from ratios of pressures; the standard reference pressure for underwater sound is 1 microPascal (µPa); for airborne sound, the standard reference pressure is 20 µPa (Richardson et al., 1995).
Acousticians have adopted a logarithmic scale for sound intensities, which is denoted in decibels (dB). Decibel measurements represent the ratio between a measured pressure value and a reference pressure value (in this case 1 µPa or, for airborne sound, 20 µPa). The logarithmic nature of the scale means that each 10-dB increase is a ten-fold increase in acoustic power (and a 20-dB increase is then a 100-fold increase in power; and a 30-dB increase is a 1,000-fold increase in power). A ten-fold increase in acoustic power does not mean that the sound is perceived as being ten times louder, however. Humans perceive a 10-dB increase in sound level as a doubling of loudness, and a 10-dB decrease in sound level as a halving of loudness. The term “sound pressure level” implies a decibel measure and a reference pressure that is used as the denominator of the ratio. Throughout this document, NMFS uses 1 microPascal (denoted re: 1µPa) as a standard reference pressure unless noted otherwise.
It is important to note that decibel values underwater and decibel values in air are not the same (different reference pressures and densities/sound speeds between media) and should not be directly compared. Because of the different densities of air and water and the different decibel standards (i.e., reference pressures) in air and water, a sound with the same level in air and in water would be approximately 62 dB lower in air. Thus, a sound that measures 160 dB (re 1 µPa) underwater would have the same approximate effective level as a sound that is 98 dB (re 20 µPa) in air.
Sound frequency is measured in cycles per second, or Hertz (abbreviated Hz), and is analogous to musical pitch; high-pitched sounds contain high frequencies and low-pitched sounds contain low frequencies. Natural sounds in the ocean span a huge range of frequencies: from earthquake noise at 5 Hz to harbor porpoise clicks at 150,000 Hz (150 kHz). These sounds are so low or so high in pitch that humans cannot even hear them; acousticians call these infrasonic (typically below 20 Hz) and ultrasonic (typically above 20,000 Hz) sounds, respectively. A single sound may be made up of many different frequencies together. Sounds made up of only a small range of frequencies are called “narrowband”, and sounds with a broad range of frequencies are called “broadband”; explosives are an example of a broadband sound source and active tactical sonars are an example of a narrowband sound source.
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 behavioral protocols or auditory evoked potential (AEP) 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. Further, the frequency range in which each group's hearing is estimated as being most sensitive is represented in the flat part of the M-weighting functions (which are derived from the audiograms described above; see Figure 1 in Southall et al., 2007) developed for each broad group. The functional groups and the associated frequencies are indicated below (though, again, 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—functional hearing is estimated to occur between approximately 7 Hz and 30 kHz;
- Mid-frequency cetaceans—functional hearing is estimated to occur between approximately 150 Hz and 160 kHz;
- High-frequency cetaceans—functional hearing is estimated to occur between approximately 200 Hz and 180 kHz;
- Pinnipeds in water—functional hearing is estimated to occur between approximately 75 Hz and 75 kHz.
The estimated hearing range for low-frequency cetaceans has been extended slightly from previous analyses (from 22 to 30 kHz). This decision is based on data from Watkins et al. (1986) for numerous mysticete species, Au et al. (2006) for humpback whales, an abstract from Frankel (2005) and paper from Lucifredi and Stein (2007) on gray whales, and an unpublished report (Ketten and Mountain, 2009) and abstract (Tubelli et al., 2012) for minke whales. As more data from more species and/or individuals become available, these estimated hearing ranges may require modification.
When sound travels (propagates) from its source, its loudness decreases as the distance traveled by the sound increases. Thus, the loudness of a sound at its source is higher than the loudness of that same sound a kilometer away. Acousticians often refer to the loudness of a sound at its source (typically referenced to one meter from the source) as the source level and the loudness of sound elsewhere as the received level (i.e., typically the receiver). For example, a humpback whale 3 km from a device that has a source level of 230 dB may only be exposed to sound that is 160 dB loud, depending on how the sound travels through water (e.g., spherical spreading [3 dB reduction with doubling of distance] was used in this example). As a result, it is important to understand the difference between source levels and received levels when discussing the loudness of sound in the ocean or its impacts on the marine environment.
As sound travels from a source, its propagation in water is influenced by various physical characteristics, including water temperature, depth, salinity, and surface and bottom properties that cause refraction, reflection, absorption, and scattering of sound waves. Oceans are not homogeneous and the contribution of each of these individual factors is extremely complex and interrelated. The physical characteristics that determine the sound's speed through the water will change with depth, season, geographic location, and with time of day (as a result, in actual active sonar operations, crews will measure oceanic conditions, such as sea water temperature and depth, to calibrate models that determine the path the sonar signal will take as it travels through the ocean and how strong the sound signal will be at a given range along a particular transmission path). As sound travels through the ocean, the intensity associated with the wavefront diminishes, or attenuates. This decrease in intensity is referred to as propagation loss, also commonly called transmission loss.
Metrics Used in This Document Back to Top
This section includes a brief explanation of the two sound measurements (sound pressure level (SPL) and sound exposure level (SEL)) frequently used to describe sound levels in the discussions of acoustic effects in this document.
Sound pressure level (SPL)—Sound pressure is the sound force per unit area, and is usually measured in micropascals (µPa), where 1 Pa is the pressure resulting from a force of one newton exerted over an area of one square meter. SPL is expressed as the ratio of a measured sound pressure and a reference level.
SPL (in dB) = 20 log (pressure/reference pressure)
The commonly used reference pressure level in underwater acoustics is 1 µPa, and the units for SPLs are dB re: 1 µPa. SPL is an instantaneous pressure measurement and can be expressed as the peak, the peak-peak, or the root mean square (rms). Root mean square pressure, which is the square root of the arithmetic average of the squared instantaneous pressure values, is typically used in discussions of the effects of sounds on vertebrates and all references to SPL in this document refer to the root mean square. SPL does not take the duration of exposure into account.
Sound exposure level (SEL)—SEL is an energy metric that integrates the squared instantaneous sound pressure over a stated time interval. The units for SEL are dB re: 1 µPa  -s. Below is a simplified formula for SEL.
SEL = SPL + 10log(duration in seconds)
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). Sound generated by impact pile driving is highly variable, based on site-specific conditions such as substrate, water depth, and current. Sound levels may also vary based on the size of the pile, the type of pile, and the energy of the hammer.
Vibratory hammers install piles by vibrating them and allowing the weight of the hammer to push them into the sediment. Vibratory hammers produce much 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). However, vibratory hammers cannot be used in all circumstances. In some substrates, the capacity of a vibratory hammer may be insufficient to drive the pile to load-bearing capacity or depth (Caltrans, 2009). Additionally, some vibrated piles must be `proofed' (i.e., struck with an impact hammer) for several seconds to several minutes in order to verify the load-bearing capacity of the pile (WSDOT, 2008).
Impact and vibratory pile driving are the primary in-water construction activities associated with the project. The sounds produced by these activities fall into one of two sound types: pulsed and non-pulsed (defined in next paragraph). Impact pile driving produces pulsed sounds, while vibratory pile driving produces non-pulsed sounds. The distinction between these two general sound types is important because they have differing potential to cause physical effects, particularly with regard to hearing (e.g., Ward, 1997 in Southall et al., 2007). Southall et al. (2007) provides an in-depth discussion of these concepts and a summary is provided here.
Pulsed sounds (e.g., explosions, gunshots, sonic booms, seismic pile driving pulses, and impact pile driving) are brief, broadband, atonal transients (ANSI, 1986; Harris, 1998) and occur either as isolated events or repeated in some succession. Pulsed sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a decay period that may include a period of diminishing, oscillating maximal and minimal pressures. Pulsed sounds generally have an increased capacity to induce physical injury as compared with sounds that lack these features.
Non-pulsed sounds (which may be intermittent or continuous) 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.
Sound Thresholds Back to Top
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 or injury 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 high levels of 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 non-pulsed sound (e.g., vibratory pile driving), but below injurious thresholds. However, due to ongoing anthropogenic noise around Elliott Bay, the ambient sound level is higher than 120 dB in this region. Based on underwater sound measurements performed by the Washington State Department of Transportation in 2011, and following NMFS Northwest Region and Northwest Fisheries Science Center's “Guidance Document: Data Collection Methods to Characterize Underwater Background Sound Relevant to Marine Mammals in Coastal Nearshore Waters and Rivers of Washington and Oregon,” we assume that the ambient sound level around the proposed project area is 123 dB (Laughlin, 2011). Therefore, 123 dB rms is used to estimate Level B harassment for non-pulsed sound (e.g., vibratory pile driving) in this instance. 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
The extent of project-generated sound both in and over water was calculated for the locations where pile driving would occur in Elliott Bay. In the absence of site-specific data, the practical spreading loss model was used for determining the extent of sound from a source (Davidson, 2004; Thomsen et al., 2006). The model assumes a logarithmic coefficient of 15, which equates to sound energy decreasing by 4.5 dB with each doubling of distance from the source. To calculate the loss of sound energy from one distance to another, the following formula is used:
Transmission Loss (dB) = 15 log(D 1/D 0)
D 1 is the distance from the source for which SPLs need to be known, and D 0 is the distance from the source for which SPLs are known (typically 10 m from the pile). This model also solves for the distance at which sound attenuates to various decibel levels (e.g., a threshold or background level). The following equation solves for distance:
D 1= D 0× 10 (TL/15)
where TL stands for transmission loss (the difference in decibel levels between D 0 and D 1). For example, using the distance to an injury threshold (D 1), the area of effect is calculated as the area of a circle, πr  , where r (radius) is the distance to the threshold or background. If a landform or other shadowing element interrupts the spread of sound within the threshold distance, then the area of effect truncates at the location of the shadowing element.
Sound levels are highly dependent on environmental site conditions. Therefore, published hydroacoustic monitoring data for projects with similar site conditions as the Elliott Bay Seawall project were considered (Caltrans, 2009 and WSDOT, 2011a). Based on these data and the noise attenuation practical spreading model, also used for pile driving activities done by the Washington State Department of Transportation and the Washington State Ferries, the sound attenuation distances summarized in Table 5 have been identified for in-water pile installation. Distance thresholds that account for each pile-related activity and pile type proposed for the Elliott Bay Seawall project are presented in Table 6.
|Pile type and approximate size||Method||Relative water depth (m)||Average sound pressure measured in dB|
|Creosote-treated 14-inch-diameter timber pile||Vibratory removal||15||164||150|
|16.5-inch-diameter precast concrete octagonal pile||Impact||15||188||176|
|Steel sheet pile pair; 48-inches in length per pair||Vibratory (installation and removal)||15||182||165|
|Steel sheet pile pair; 48-inches in length per pair||Impact (installation proofing)||15||205||190|
|Harassment threshold||Distance to harassment for pinnipeds||Distance to harassment for cetaceans|
|24-inch Steel Sheet Pile (vibratory)|
|Level A (180 and 190 dB)||0.2 m (0.7 ft)||1 m (3.3 ft).|
|Level B (123 dB)||6,276 m (3.9 mi)||6,276 m (3.9 mi).|
|24-inch Steel Sheet Pile (impact, unattenuated)|
|Level A (180 and 190 dB)||10 m (33 ft)||46 m (152 ft).|
|Level B (160 dB)||1,000 m (3,280 ft)||1,000 m (3,280 ft).|
|24-inch Concrete Pile (impact, unattenuated)|
|Level A (180 and 190 dB)||1 m (3.3 ft)||5 m (18 ft).|
|Level B (160 dB)||117 m (383 ft)||117 m (383 ft).|
|24-inch Concrete Pile (impact, unattenuated)|
|Level A (180 and 190 dB)||0.5 m (1.8 ft)||2.5 m (8.2 ft).|
|Level B (160 dB)||54 m (177 ft)||54 m (177 ft).|
Most distances to Level A thresholds (for vibratory steel sheet pile and impact concrete pile installations) were calculated to be very close to the sound source. In other words, the only way a marine mammal could be injured by elevated noise levels from pile-related activities would be if the animal was located immediately adjacent to the pile being driven. However, longer distances to Level A thresholds were calculated for impact pile installation for steel sheet piles: 152 ft for cetaceans and 33 ft for pinnipeds. Proposed mitigation and monitoring measures (discussed later in this document) would make the potential for injury unlikely.
Description of Marine Mammals in the Area of the Specified Activity Back to Top
Nine marine mammal species, including distinct population segments, have the potential to occur in the area of the specified activity (Table 7). All nine species have been observed in Puget Sound at certain periods of the year and are discussed in further detail below.
|Common name||Scientific name||ESA status||MMPA status||Abundance||Population status||Likelihood of occurrence||Seasonality|
|Pacific harbor seal||Phoca vitulina||n/a||unknown||Occasional||Year-round|
|California sea lion||Zalophus californianus||296,750||Occasional||August-April.|
|Steller sea lion||Eumetopias jubatus||Threatened||Depleted||58,334-72,223||increasing||Rare||August-April.|
|Harbor porpoise||Phocoena phocoena||unknown||unknown||Rare||Year-round.|
|Dall's porpoise||Phocoenoides dalli||42,000||unknown||Rare||Winter-Spring.|
|Southern resident killer whale DPS||Orcinus orca||Endangered||86||unknown||Occasional||Year-round.|
|Transient killer whale||Orcinus orca||346||unknown||Rare||Year-round.|
|Humpback whale||Megaptera novaengliae||Endangered||Depleted||2,043||increasing||Rare||February-June.|
|Gray whale||Eschrichtius robustus||18,000||increasing||Rare||January-September.|
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. 2007b). The seals that could potentially be in the project area are from the inland waters of Washington stock.
The average weight for adult seals is about 180 lb (82 kg) and males are typically 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—In 1999, the mean count of harbor seals occurring in Washington's inland waters was 9,550 animals (Jeffries et al., 2003). Radio-tagging studies conducted at six locations collected information on haulout patterns of harbor seals in 1991 and 1992, resulting in a correction factor of 1.53 to account for animals in the water that are missed during the aerial surveys (Huber et al., 2001). Using this correction factor results in a population estimate of 14,612 for the Washington inland waters stock of harbor seals (Jeffries et al., 2003). Although this abundance estimate represents the best scientific information available, per NMFS stock assessment policy it is not considered current because it is more than 8 years old. Between 1983 and 1996, the annual rate of increase for this stock was 6 percent (Jeffries et al., 1997). The peak count occurred in 1996 and, based on a fitted generalized logistic model, the population is thought to be stable. Because there is no current estimate of minimum abundance, potential biological removal (PBR) cannot be calculated for this stock. Harbor seals are not considered to be depleted under the MMPA or listed as threatened or endangered under ESA.
Behavior and Ecology—Harbor seals are non-migratory with local movements associated with such factors as tides, weather, season, food availability, and reproduction (Scheffer and Slipp, 1944; Fisher, 1952; Bigg, 1969, 1981). They are not known to make extensive pelagic migrations, although some long distance movement of tagged animals in Alaska (174 km), and along the U.S. west coast (up to 550 km), have been recorded (Pitcher and McAllister, 1981; Brown and Mate, 1983; Herder, 1986). 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).
Harbor seals haul out on rocks, reefs, beaches, and ice and feed in marine, estuarine, and occasionally fresh waters. Harbor seals display strong fidelity for haul-out sites (Pitcher and Calkins, 1979; Pitcher and McAllister, 1981), although human disturbance can affect haul-out choice (Harris et al., 2003). Group sizes range from small numbers of animals on intertidal rocks to several thousand animals found seasonally in coastal estuaries. The harbor seal is the most commonly observed and widely distributed pinniped found in Washington (Jeffries et al., 2000; ODFW, 2010). Harbor seals use hundreds of sites to rest or haul out along the coast and inland waters of Washington, including tidal sand bars and mudflats in estuaries, intertidal rocks and reefs, beaches, log booms, docks, and floats in all marine areas of the state.
The harbor seal is the only pinniped species that is found year-round and breeds in Washington waters (Jeffries et al., 2000). Harbor seals mate at sea and females give birth during the spring and summer, although the pupping season varies by latitude. Pupping seasons vary by geographic region with pups born in the San Juan Islands and eastern bays of Puget Sound from June through August. Suckling harbor seal pups spend as much as forty percent of their time in the water (Bowen et al., 1999).
Individuals occur along the Elliott Bay shoreline (WSDOT, 2004). There is one documented harbor seal haul-out area of less than 100 animals near Bainbridge Island, about six miles from the proposed region of activity and outside of the area of potential effects. The haul-out consists of intertidal rocks and reef areas around Blakely Rocks (Jeffries et al., 2000).
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 have 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 dB 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 Schusterman (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 within that band. They are most sensitive at frequencies below 50 kHz; above 60 kHz sensitivity rapidly decreases.
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 breeding areas of the California sea lion are on islands located in southern California, western Baja California, and the Gulf of California (Carretta et al., 2007). These three geographic regions are used to separate this subspecies into three stocks: (1) The U.S. stock begins at the U.S./Mexico border and extends northward into Canada, (2) the Western Baja California stock extends from the U.S./Mexico border to the southern tip of the Baja California peninsula, and (3) the Gulf of California stock which includes the Gulf of California from the southern tip of the Baja California peninsula and across to the mainland and extends to southern Mexico (Lowry et al., 1992).
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 5 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 entire population of California sea lions cannot be counted because all age and sex classes are not ashore at the same time. Therefore, pups are counted during the breeding season and the number of births is estimated from the pup count. The size of the population is then estimated from the number of births and the proportion of pups in the population. This most recently resulted in a population estimate of 296,750 animals. The PBR level for this stock is 9,200 sea lions per year. California sea lions are not considered to be depleted under the MMPA or listed as threatened or endangered under ESA.
Behavior and Ecology—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 in the California Channel Islands (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 to 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). During 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 do not breed in Washington, but are typically observed in Washington between August and April, after they have dispersed from breeding colonies.
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 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 4-5 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.
The California sea lion is the most frequently sighted pinniped found in Washington waters and uses haul-out sites along the outer coast, Strait of Juan de Fuca, and in Puget Sound. Haul-out sites are located on jetties, offshore rocks and islands, log booms, marine docks, and navigation buoys. This species is also frequently seen resting in the water together in groups in Puget Sound (Jeffries et al., 2000). There are three documented California sea lion haul-outs near the proposed project area; all are located about six miles away and outside of the area of potential effects. These haul-outs include a yellow `T' buoy off Alki Point, a yellow `SG' buoy between West Point and Skiff Point, and a red buoy off Restoration Point (Jeffries et al., 2000). The haul-outs have all been identified to have populations less than 100 individuals. It is assumed that California sea lions seen in and around the proposed project area use these haul-outs.
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 of these underwater sounds have most of their energy below 4 kHz (Schusterman et al., 1967).
The range of maximal hearing sensitivity for California sea lions 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).
Steller Sea Lions
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 about 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. Animals found in the proposed project area would be from the eastern DPS (NMFS, 1997a; Loughlin, 2002; Angliss and Outlaw, 2005).
Status—Steller sea lions were listed as threatened range-wide under the ESA in 1990. After division into two DPSs, the western DPS was listed as endangered under the ESA in 1997, while the eastern DPS remained classified as threatened. The eastern DPS breeds in rookeries located in southeast Alaska, British Columbia, Oregon, and California. While some pupping has been reported recently along the coast of Washington, there are no active rookeries in Washington. A final revised species recovery plan addresses both DPSs (NMFS, 2008a).
NMFS designated critical habitat 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 (900 m) 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, Southeast Farallon, and Sugarloaf Island and Cape Mendocino) are designated critical habitat (NMFS, 1993). There is no designated critical habitat within the proposed project area.
Factors that have previously been identified as threats to 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. Steller sea lions are also sensitive to disturbance at rookeries (during pupping and breeding) and haul-out sites.
The Recovery Plan for the Steller Sea Lion (NMFS, 2008a) states that the overall abundance of Steller sea lions in the eastern DPS has increased for a sustained period of at least three decades, and that pup production has increased significantly, especially since the mid-1990s. Between 1977 and 2002, researchers estimated that overall abundance of the eastern DPS had increased at an average rate of 3.1 percent per year (NMFS, 2008a; Pitcher et al., 2007). NMFS' most recent stock assessment report estimates that population for the eastern DPS is a minimum of 52,847 individuals; this estimate is not corrected for animals at sea, and actual population is estimated to be within the range 58,334 to 72,223 (Allen and Angliss, 2010). The minimum count for Steller sea lions in Washington was 516 in 2001 (Pitcher et al., 2007).
In the far southern end of Steller sea lion range (Channel Islands in southern California), population declined significantly after the 1930s—probably due to hunting and harassment (Bartholomew and Boolootian, 1960; Bartholomew, 1967)—and several rookeries and haul-outs have been abandoned. The lack of recolonization at the southernmost portion of the range (e.g., San Miguel Island rookery), despite stability in the non-pup portion of the overall California population, is likely a response to a suite of factors including changes in ocean conditions (e.g., warmer temperatures) that may be contributing to habitat changes that favor California sea lions over Steller sea lions (NMFS, 2007) and competition for space on land, and possibly prey, with species that have experienced explosive growth over the past three decades (e.g., California sea lions and northern elephant seals [Mirounga angustirostris]). Although recovery in California has lagged behind the rest of the DPS, this portion of the DPS' range has recently shown a positive growth rate (NMML, 2012). While non-pup counts in California in the 2000s are only 34 percent of pre-decline counts (1927-1947), the population has increased significantly since 1990. Despite the abandonment of certain rookeries in California, pup production at other rookeries in California has increased over the last 20 years and, overall, the eastern DPS has increased at an average annual growth rate of 4.3 percent per year for 30 years. Even though these rookeries might not be recolonized, their loss has not prevented the increasing abundance of Steller sea lions in California or in the eastern DPS overall.
Because the eastern DPS of Steller sea lion is currently listed as threatened under the ESA, it is therefore designated as depleted and classified as a strategic stock under the MMPA. However, the eastern DPS 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 observed annual rates of increase. 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 the eastern stock has been consistent and long-term, and may indicate that this stock is reaching OSP.
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 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 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).
The nearest Steller sea lion haul-out to the proposed project area is about six miles away and outside the area of potential effects. This haul-out is composed of net pens offshore of the south end of Bainbridge Island. The population of Steller sea lions at this haul-out has been estimated at less than 100 individuals (Jeffries et al., 2000). Review of many anecdotal accounts indicates that this species is rarely seen in the area of potential effects.
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).
Species Description—Harbor porpoises inhabit northern temperate and subarctic coastal and offshore waters. They are commonly found in bays, estuaries, harbors, and fjords less than 650 ft (200 m) deep. In the North Atlantic, they range from West Greenland to Cape Hatteras, North Carolina and from the Barents Sea to West Africa. In the North Pacific, they are found from Japan north to the Chukchi Sea and from Monterey Bay, California to the Beaufort Sea. There are ten stocks of harbor porpoises in U.S. waters: Bering Sea, Gulf of Alaska, Gulf of Maine-Bay of Fundy, Inland Washington, Monterey Bay, Morro Bay, Northern California-Southern Oregon, Oregon-Washington Coastal, San Francisco-Russian River, and Southeast Alaska. Harbor porpoises that could potentially be in the proposed project area would be part of the Inland Washington stock.
Harbor porpoises have a small, robust body with a short, blunt beak. They typically weigh 135-170 pounds and are about 5 to 5.5 ft (1.5 to 1.7 m) in length. Females are slightly larger than males. All animals are dark gray with a white underside.
Status—Aerial surveys of the Strait of Juan de Fuca, San Juan Islands, Gulf Islands, and Strait of Georgia (which includes waters inhabited by the Washington Inland stock of harbor porpoise) were conducted during August of 2002 and 2003. The average abundance estimate resulting from those surveys is 3,123. When corrected for availability and perception bias, the estimated abundance for the Washington Inland stock in 2002/2003 is 10,682 animals. However, because the most recent abundance estimate is more than 8 years old, there is no current estimate of abundance available for this stock. Because there is no current estimate of minimum abundance, a PBR cannot be calculated for this stock. There is also no reliable data on long-term population trends of harbor porpoise for most waters of Oregon, Washington, or British Columbia. Harbor porpoises are not considered to be depleted under the MMPA or listed as threatened or endangered under the ESA.
Behavior and Ecology—Harbor porpoises are known to occur year-round in the inland trans-boundary waters of Washington and British Columbia and along the Oregon/Washington coast. Although differences in density exist between coastal Oregon/Washington and inland Washington waters, a specific stock boundary line cannot be identified based on biological or genetic differences. However, harbor porpoise movements and rates of intermixing within the eastern North Pacific are restricted, and there has been a significant decline in harbor porpoise sightings within southern Puget Sound since the 1940s, and today, harbor porpoise are rarely observed. Recently, there have been confirmed sightings of harbor porpoise in central Puget Sound (NMFS, 2006); however, no reports of harbor porpoises in the area of potential effects were made during 2011 (Whale Museum, 2011).
Harbor porpoises are non-social animals usually seen in groups of two to five animals. They feed on demersal and benthic species, mainly schooling fish and cephalopods.
Acoustics—Harbor porpoises are considered high-frequency cetaceans and their estimated auditory bandwidth ranges from 200 Hz to 180 kHz. Some studies suggest that harbor porpoises may be more sensitive to sound than other odontocetes (Lucke et al., 2009; Kastelein et al., 2011). In general, toothed whales produce a wide variety of sounds, which include species-specific broadband “clicks” with peak energy between 10 and 200 kHz, individually variable “burst pulse” click trains, and constant frequency or frequency-modulated (FM) whistles ranging from 4 to 16 kHz (Wartzok and Ketten, 1999). The general consensus is that the tonal vocalizations (whistles) produced by toothed whales play an important role in maintaining contact between dispersed individuals, while broadband clicks are used during echolocation (Wartzok and Ketten, 1999). Burst pulses have also been strongly implicated in communication, with some scientists suggesting that they play an important role in agonistic encounters (McCowan and Reiss, 1995), while others have proposed that they represent “emotive” signals in a broader sense, possibly representing graded communication signals (Herzing, 1996). Sperm whales, however, are known to produce only clicks, which are used for both communication and echolocation (Whitehead, 2003). Most of the energy of toothed whale social vocalizations is concentrated near 10 kHz, with source levels for whistles as high as 100 to 180 dB re 1 μPa at 1 m (Richardson et al., 1995). No odontocete has been shown audiometrically to have acute hearing (<80 dB re 1 μPa) below 500 Hz (DoN, 2001). Sperm whales produce clicks, which may be used to echolocate (Mullins et al., 1988), with a frequency range from less than 100 Hz to 30 kHz and source levels up to 230 dB re 1 μPa 1 m or greater (Mohl et al., 2000).
Species Description—Dall's porpoises are common in the North Pacific Ocean, preferring temperate or cooler waters that are more than 600 ft (180 m) deep and with temperatures between 36-63 degrees Fahrenheit. For management purposes, Dall's porpoises inhabiting U.S. waters have been divided into two stocks: the Alaska stock and the California/Oregon/Washington stock. Dall's porpoises that could potentially be in the project area would be from the California/Oregon/Washington stock.
Dall's porpoises are fast swimming members of the porpoise family. They can weigh up to 480 pounds and grow up to 8 ft (2.4 m) long. They are identified by a dark gray or black body with variable contrasting white panels. These markings and colorations vary with geographic location and life stage.
Status—Dall's porpoise distribution in this region is highly variable between years and appears to be affected by oceanographic conditions. The most recent abundance estimate (42,000 animals) relies on estimates from 2005 and 2008 vessel-based line transect surveys off the coasts of California, Oregon, and Washington. Insufficient data are available to estimate current population trends. However, Dall's porpoises are generally considered reasonably abundant. There are an estimated 130,000 individuals in U.S. waters, including 76,000-99,500 off the Pacific coast (California, Oregon, and Washington) (NMFS, 2012). The PBR level for this stock is 257 animals per year. Dall's porpoises are not considered depleted under the MMPA or listed as threatened or endangered under the ESA.
Behavior and Ecology—Dall's porpoises can be found in offshore, inshore, and nearshore oceanic waters and are endemic to temperate waters of the North Pacific Ocean. Off the west coast, they are commonly seen in shelf, slope, and offshore waters. Sighting patterns from aerial and shipboard surveys conducted in California, Oregon, and Washington at different times suggest that north-south movement between these states occurs as oceanographic conditions change, both on seasonal and inter-annual scales. Only rarely have reports of Dall's porpoises been made for the area of potential effects. They feed on small schooling fish, mid- and deep-water fish, cephalopods, and occasionally crabs and shrimp. Feeding usually occurs at night when their prey vertically migrates up toward the water's surface. Dall's porpoises are capable of diving up to 1,640 ft (500 m) in order to reach their prey.
Acoustics—Dall's porpoises are considered high-frequency cetaceans their estimated auditory bandwidth ranges from 200 Hz to 180 kHz. General acoustic information on toothed whales was provided in the Harbor Porpoise section and is not repeated here.
Species Description—Killer whales are the most widely distributed cetacean species in the world. Killer whales prefer colder waters, with the greatest abundances found within 800 km of major continents. Along the west coast of North America, killer whales occur along the entire Alaskan coast, in British Columbia and Washington inland waterways, and along the outer coasts of Washington, Oregon, and California. Based on morphology, ecology, genetics, and behavior, pods have been labeled as `resident,' `transient,' and `offshore.' The distinct population segment of Southern resident killer whales is expected to have the highest potential of occurrence in the proposed project area. Transient killer whales may occasionally occur and are discussed where appropriate.
Killer whales are members of the dolphin family and can grow as long as 32 ft (9.8 m) and weigh as much as 22,000 pounds. They are identified by their large size and distinctive black and white appearance. Killer whales are highly social animals and often travel in groups of up to 50 animals. However, the Southern resident DPS is made up of three pods, and the one most likely to occur in the proposed project area—the J pod—has about 26 animals.
Status—The Eastern North Pacific Southern Resident stock is a trans-boundary stock including killer whales in inland Washington and southern British Columbia waters. Photo- identification of individual whales through the years has resulted in a substantial understanding of this stock's structure, behaviors, and movements. In 1993, the three pods comprising this stock totaled 96 killer whales (Ford et al., 1994). The population increased to 99 whales in 1995, then declined to 79 whales in 2001, and most recently number 86 whales in 2010 (Ford et al., 2000, Center for Whale Research, unpubl. data).
The Southern Resident killer whale is listed as endangered under the ESA and as strategic under the MMPA. Critical habitat was designated in 2006 and includes all marine waters greater than 20 ft in depth. Critical habitat for this DPS includes the summer core area in Haro Strait and waters around the San Juan Islands; Puget Sound; and the Strait of Juan de Fuca (NOAA, 2006). On November 27, 2012, NMFS announced a 90-day finding on a petition to delist the Southern Resident killer whale DPS (77 FR 70733, November 27, 2012). NMFS found that the petition action may be warranted and initiated a status review of Southern Resident killer whales to determine further action. The request for information period closed on January 28, 2013 and NMFS has not yet made a determination. Transient killer whales are not listed under the ESA, but are considered depleted under the MMPA.
Behavior and Ecology—Killer whales feed on a variety of fish, marine mammals, and sharks, depending on their population and geographic location. Resident populations in the eastern North Pacific feed mainly on salmonids, such as Chinook and chum salmon.
A long-term database maintained by the Whale Museum monitors sightings and geospatial locations of Southern Resident killer whale, among other marine mammals, in inland waters of Washington State. Data are largely based on opportunistic sightings from a variety of sources (i.e., public reports, commercial whale watching, Soundwatch, Lime Kiln State Park land-based observations, and independent research reports), but are regarded as a robust but difficult to quantify inventory of occurrences. The data provide the most comprehensive assemblage of broad-scale habitat use by the DPS in inland waters.
Based on reports from 1990 to 2008, the greatest number of unique killer whale sighting-days near or in the area of potential effects occurred from November through January, although observations were made during all months except May (Osborne, 2008). Most observations were of Southern Resident killer whales passing west of Alki Point (82 percent of all observations), which lies on the edge or outside the area of potential effects; a pattern potentially due to the high level of human disturbance or highly degraded habitat features currently found within Elliott Bay. Of the pods that compose this DPS, the J pod, with an estimated 26 members, is the pod most likely to appear year-round near the San Juan Islands, in the lower Puget Sound near Seattle, and in Georgia Strait at the mouth of the Fraser River. The J pod tends to frequent the west side of San Juan Island in mid to late spring (CWR, 2011). An analysis of 2011 sightings described an estimated 93 sightings of Southern Resident killer whales near the area of potential effects (Whale Museum, 2011). During this same analysis period, 12 transient killer whales were also observed near the area of potential effects. The majority of all sightings in this area are of groups of killer whales moving through the main channel between Bainbridge Island and Elliott Bay and outside the area of potential effects (Whale Museum, 2011). The purely descriptive format of these observations make it impossible to discern what proportion of the killer whales observed entered into the area of potential effects; however, it is assumed individuals may enter into this area on occasion.
Acoustics—Killer whales are considered mid-frequency cetaceans and their estimated auditory bandwidth ranges from 150 Hz to 160 kHz. General acoustics information for toothed whales was provided in the Harbor Porpoise section and is not repeated here.
Species Description—Humpbacks are large, dark grey baleen whales with some areas of white. They can grow up to 60 ft (18 m) long and weigh up to 40 tons. They are well known for their long pectoral fins, which can reach up to 15 ft (4.6 m) in length. Humpback whales live in all major oceans from the equator to sub-polar latitudes.
In the North Pacific, there are at least three separate populations: the California/Oregon/Washington stock, the Central North Pacific stock, and the Western North Pacific stock. Any humpbacks that may occur in the proposed project area would be part of the California/Oregon/Washington stock.
Status—The best estimate of abundance for the California/Oregon/Washington stock is 2,043 animals and based on a mark-recapture study. Ship surveys provide some indication that humpback whales increased in abundance in California coastal waters between 1979-1980 and 1991 (Barlow, 1994) and between 1991 and 2005 (Barlow and Forney, 2007; Forney, 2007), but this increase was not steady, and estimates showed a slight dip in 2001. Mark-recapture population estimates have shown a long-term increase of about 7.5 percent per year (Calambokidis, 2009), although there have been short-term declines during this period, probably due to oceanographic variability. Population estimates for the entire North Pacific have also increased substantially and the growth rate implied by these estimates (6-7 percent) is consistent with the recently observed growth rate of the California/Oregon/Washington stock (NMFS, 2011).
As a result of commercial whaling, humpback whales are listed as endangered under the ESA throughout their range and also considered depleted under the MMPA.
Behavior and Ecology—Humpback whales complete the farthest migration of any mammal each year. During the summer months, the California/Oregon/Washington stock spends the majority of their time feeding along the coast of North America. Humpback whales filter feed on tiny crustaceans (mostly krill), plankton, and small fish. This stock then spends winter in coastal Central America and Mexico engaging in mating activities.
Humpback whales are found in coastal waters of Washington as they migrate from feeding grounds to winter breeding grounds. Humpback whales are considered rare visitors to Puget Sound and are not observed in the area every year. Past sightings around Puget Sound and Hood Canal have taken place well away from the proposed project area; however, it is possible that they may occur at least once during the proposed construction period.
Acoustics—Baleen whale vocalizations are composed primarily of frequencies below 1 kHz, and some contain fundamental frequencies as low as 16 Hz (Watkins et al., 1987; Richardson et al., 1995; Rivers, 1997; Moore et al., 1998; Stafford et al., 1999; Wartzok and Ketten, 1999) but can be as high as 24 kHz for humpback whales (Au et al., 2006). Clark and Ellison (2004) suggested that baleen whales use low-frequency sounds not only for long-range communication, but also as a simple form of echo ranging, using echoes to navigate and orient relative to physical features of the ocean. Information on auditory function in baleen whales is extremely lacking. Sensitivity to low-frequency sound by baleen whales has been inferred from observed vocalization frequencies, observed reactions to playback of sounds, and anatomical analyses of the auditory system. Although there is apparently much variation, the source levels of most baleen whale vocalizations lie in the range of 150-190 dB re 1 µPa at 1 m. Low-frequency vocalizations made by baleen whales and their corresponding auditory anatomy suggest that they have good low-frequency hearing (Ketten, 2000), although specific data on sensitivity, frequency or intensity discrimination, or localization abilities are lacking.
Species Description—Gray whales are large baleen whales found mainly in shallow coastal waters of the North Pacific Ocean. They are identified by their mottled gray bodies, small eyes, and dorsal hump (not a dorsal fin). The can weigh up to 80,000 pounds and grow up to 50 ft (15 m) in length.
There are two isolated geographic distributions of gray whales in the North Pacific Ocean: the Eastern North Pacific stock and the Western North Pacific stock. Any gray whales occurring around the proposed project area would be part of the Eastern North Pacific stock, which includes the west coast of North America.
Status—Systematic counts of Eastern North Pacific gray whales migrating south along the Central California coast have been conducted by shore-based observers at Granite Canyon most years since 1967. The most recent abundance estimates are based on counts made during the 1997-1998, 2000-2001, and 2001-2002 southbound migrations, and range from about 18,000 to 30,000 animals. The population size of the Eastern North Pacific stock has been increasing over the past several decades despite an unusual mortality event in 1999 and 2000. The estimated annual rate of increase is 3.2-3.3 percent. In contrast the Western North Pacific population remains highly depleted.
While the Western North Pacific population is listed as endangered under the ESA, the Eastern North Pacific population was delisted from the ESA in 1994 after reaching a `recovered' status. The Eastern North Pacific stock is not considered depleted under the MMPA.
Behavior and Ecology—Gray whales feed in shallow waters, usually 150-400 ft deep and adults consume over 1 ton of food per day during peak feeding periods. The gray whale is unique among cetaceans as a bottom-feeder that rolls onto its side, sucking up sediment from the seabed. Benthic organisms that live in the sediment are trapped by the baleen plates as water and silt are filtered out. Gray whales typically travel alone or in small, unstable groups.
Eastern North Pacific gray whales occur frequently off the coast of Washington during their southerly migration in November and December, and northern migration from March through May (Rugh et al., 2001; Rice et al., 1984). Gray whales are observed in Washington inland waters regularly between the months of January and September, with peaks between March and May. Gray whale sightings are typically reported in February through May and include an observation of a gray whale off the ferry terminal at Pier 52 heading toward the East Waterway in March 2010 (CWR, 2011; Whale Museum, 2012). Three gray whales were observed near the project area during 2011, but the narrative format of the observations makes it difficult to discern whether these individuals entered into the area of potential effects. It is assumed that gray whales might rarely occur in the area of potential effects.
Acoustics—Gray whale vocalizations and auditory function, like all baleen whale acoustics, is similar to that of humpback whales, described above. That information is not repeated here.
Potential Effects of the Specified Activity on Marine Mammals Back to Top
SDOT's in-water construction activities (i.e., pile driving and removal) would introduce elevated levels of sound into the marine environment and have the potential to adversely impact marine mammals. The potential effects of sound from the proposed activities associated with the Elliott Bay Seawall project may include one or more of the following: tolerance; masking of natural sounds; behavioral disturbance; non-auditory physical effects; and temporary or permanent hearing impairment (Richardson et al., 1995). However, for reasons discussed later in this document, it is unlikely that there would be any cases of temporary or permanent hearing impairment resulting from these activities. As outlined in previous NMFS documents, the effects of sound on marine mammals are highly variable, and can be categorized as follows (based on Richardson et al., 1995):
- The sound may be too weak to be heard at the location of the animal (i.e., lower than the prevailing ambient sound level, the hearing threshold of the animal at relevant frequencies, or both);
- The sound may be audible but not strong enough to elicit any overt behavioral response;
- The sound may elicit reactions of varying degrees and variable relevance to the well-being of the marine mammal; these can range from temporary alert responses to active avoidance reactions such as vacating an area until the stimulus ceases, but potentially for longer periods of time;
- Upon repeated exposure, a marine mammal may exhibit diminishing responsiveness (habituation), or disturbance effects may persist; the latter is most likely with sounds that are highly variable in characteristics and unpredictable in occurrence, and associated with situations that a marine mammal perceives as a threat;
- Any anthropogenic sound that is strong enough to be heard has the potential to result in masking, or reduce the ability of a marine mammal to hear biological sounds at similar frequencies, including calls from conspecifics and underwater environmental sounds such as surf sound;
- If mammals remain in an area because it is important for feeding, breeding, or some other biologically important purpose even though there is chronic exposure to sound, it is possible that there could be sound-induced physiological stress; this might in turn have negative effects on the well-being or reproduction of the animals involved; and
- Very strong sounds have the potential to cause a temporary or permanent reduction in hearing sensitivity, also referred to as threshold shift. In terrestrial mammals, and presumably marine mammals, received sound levels must far exceed the animal's hearing threshold for there to be any temporary threshold shift (TTS). For transient sounds, the sound level necessary to cause TTS is inversely related to the duration of the sound. Received sound levels must be even higher for there to be risk of permanent hearing impairment (PTS). In addition, intense acoustic or explosive events may cause trauma to tissues associated with organs vital for hearing, sound production, respiration and other functions. This trauma may include minor to severe hemorrhage.
Numerous studies have shown that underwater sounds from industrial activities are often readily detectable by marine mammals in the water at distances of many kilometers. However, other studies have shown that marine mammals at distances more than a few kilometers away often show no apparent response to industrial activities of various types (Miller et al., 2005). This is often true even in cases when the sounds must be readily audible to the animals based on measured received levels and the hearing sensitivity of that mammal group. Although various baleen whales, toothed whales, and (less frequently) pinnipeds have been shown to react behaviorally to underwater sound from sources such as airgun pulses or vessels under some conditions, at other times, mammals of all three types have shown no overt reactions (e.g., Malme et al., 1986; Richardson et al., 1995; Madsen and Mohl, 2000; Croll et al., 2001; Jacobs and Terhune, 2002; Madsen et al., 2002; Miller et al., 2005). In general, pinnipeds seem to be more tolerant of exposure to some types of underwater sound than are baleen whales. Richardson et al. (1995) found that vessel sound does not seem to strongly affect pinnipeds that are already in the water. Richardson et al. (1995) went on to explain that seals on haul-outs sometimes respond strongly to the presence of vessels and at other times appear to show considerable tolerance of vessels, and Brueggeman et al. (1992) observed ringed seals (Pusa hispida) hauled out on ice pans displaying short-term escape reactions when a ship approached within 0.16-0.31 mi (0.25-0.5 km).
Masking is the obscuring of sounds of interest to an animal by other sounds, typically at similar frequencies. Marine mammals are highly dependent on sound, and their ability to recognize sound signals amid other sound is important in communication and detection of both predators and prey. Background ambient sound may interfere with or mask the ability of an animal to detect a sound signal even when that signal is above its absolute hearing threshold. Even in the absence of anthropogenic sound, the marine environment is often loud. Natural ambient sound includes contributions from wind, waves, precipitation, other animals, and (at frequencies above 30 kHz) thermal sound resulting from molecular agitation (Richardson et al., 1995).
Background sound may also include anthropogenic sound, and masking of natural sounds can result when human activities produce high levels of background sound. Conversely, if the background level of underwater sound is high (e.g., on a day with strong wind and high waves), an anthropogenic sound source would not be detectable as far away as would be possible under quieter conditions and would itself be masked. Ambient sound is highly variable on continental shelves (Thompson, 1965; Myrberg, 1978; Chapman et al., 1998; Desharnais et al., 1999). This results in a high degree of variability in the range at which marine mammals can detect anthropogenic sounds.
Although masking is a phenomenon which may occur naturally, the introduction of loud anthropogenic sounds into the marine environment at frequencies important to marine mammals increases the severity and frequency of occurrence of masking. For example, if a baleen whale is exposed to continuous low-frequency sound from an industrial source, this would reduce the size of the area around that whale within which it can hear the calls of another whale. The components of background noise that are similar in frequency to the signal in question primarily determine the degree of masking of that signal. In general, little is known about the degree to which marine mammals rely upon detection of sounds from conspecifics, predators, prey, or other natural sources. In the absence of specific information about the importance of detecting these natural sounds, it is not possible to predict the impact of masking on marine mammals (Richardson et al., 1995). In general, masking effects are expected to be less severe when sounds are transient than when they are continuous. Masking is typically of greater concern for those marine mammals that utilize low frequency communications, such as baleen whales and, as such, is not likely to occur for pinnipeds or small odontocetes in the Region of Activity.
Behavioral disturbance is one of the primary potential impacts of anthropogenic sound on marine mammals. Disturbance can result in a variety of effects, such as subtle or dramatic changes in behavior or displacement, but the degree to which disturbance causes such effects may be highly dependent upon the context in which the stimulus occurs. For example, an animal that is feeding may be less prone to disturbance from a given stimulus than one that is not. For many species and situations, there is no detailed information about reactions to sound.
Behavioral reactions of marine mammals to sound are difficult to predict because they are dependent on numerous factors, including species, maturity, experience, activity, reproductive state, time of day, and weather. If a marine mammal does react to an underwater sound by changing its behavior or moving a small distance, the impacts of that change may not be important to the individual, the stock, or the species as a whole. However, if a sound source displaces marine mammals from an important feeding or breeding area for a prolonged period, impacts on the animals could be important. In general, pinnipeds seem more tolerant of, or at least habituate more quickly to, potentially disturbing underwater sound than do cetaceans, and generally seem to be less responsive to exposure to industrial sound than most cetaceans. Pinniped responses to underwater sound from some types of industrial activities such as seismic exploration appear to be temporary and localized (Harris et al., 2001; Reiser et al., 2009).
Because the few available studies show wide variation in response to underwater and airborne sound, it is difficult to quantify exactly how pile driving sound would affect marine mammals in the area. The literature shows that elevated underwater sound levels could prompt a range of effects, including no obvious visible response, or behavioral responses that may include annoyance and increased alertness, visual orientation towards the sound, investigation of the sound, change in movement pattern or direction, habituation, alteration of feeding and social interaction, or temporary or permanent avoidance of the area affected by sound. Minor behavioral responses do not necessarily cause long-term effects to the individuals involved. Severe responses include panic, immediate movement away from the sound, and stampeding, which could potentially lead to injury or mortality (Southall et al., 2007).
Southall et al. (2007) reviewed literature describing responses of pinnipeds to non-pulsed sound in water and reported that the limited data suggest exposures between approximately 90 and 140 dB generally do not appear to induce strong behavioral responses in pinnipeds, while higher levels of pulsed sound, ranging between 150 and 180 dB, will prompt avoidance of an area. It is important to note that among these studies, there are some apparent differences in responses between field and laboratory conditions. In contrast to the mid-frequency odontocetes, captive pinnipeds responded more strongly at lower levels than did animals in the field. Again, contextual issues are the likely cause of this difference. For airborne sound, Southall et al. (2007) note there are extremely limited data suggesting very minor, if any, observable behavioral responses by pinnipeds exposed to airborne pulses of 60 to 80 dB; however, given the paucity of data on the subject, we cannot rule out the possibility that avoidance of sound in the Region of Activity could occur.
In their comprehensive review of available literature, Southall et al. (2007) noted that quantitative studies on behavioral reactions of pinnipeds to underwater sound are rare. A subset of only three studies observed the response of pinnipeds to multiple pulses of underwater sound (a category of sound types that includes impact pile driving), and were also deemed by the authors as having results that are both measurable and representative. However, a number of studies not used by Southall et al. (2007) provide additional information, both quantitative and anecdotal, regarding the reactions of pinnipeds to multiple pulses of underwater sound.
Harris et al. (2001) observed the response of ringed, bearded (Erignathus barbatus), and spotted seals (Phoca largha) to underwater operation of a single air gun and an eleven-gun array. Received exposure levels were 160 to 200 dB. Results fit into two categories. In some instances, seals exhibited no response to sound. However, the study noted significantly fewer seals during operation of the full array in some instances. Additionally, the study noted some avoidance of the area within 150 m of the source during full array operations.
Blackwell et al. (2004) is the only cited study directly related to pile driving. The study observed ringed seals during impact installation of steel pipe pile. Received underwater SPLs were measured at 151 dB at 63 m. The seals exhibited either no response or only brief orientation response (defined as “investigation or visual orientation”). It should be noted that the observations were made after pile driving was already in progress. Therefore, it is possible that the low-level response was due to prior habituation.
Miller et al. (2005) observed responses of ringed and bearded seals to a seismic air gun array. Received underwater sound levels were estimated at 160 to 200 dB. There were fewer seals present close to the sound source during air gun operations in the first year, but in the second year the seals showed no avoidance. In some instances, seals were present in very close range of the sound. The authors concluded that there was “no observable behavioral response” to seismic air gun operations.
During a Caltrans installation demonstration project for retrofit work on the East Span of the San Francisco Oakland Bay Bridge, California, sea lions responded to pile driving by swimming rapidly out of the area, regardless of the size of the pile-driving hammer or the presence of sound attenuation devices (74 FR 63724).
Jacobs and Terhune (2002) observed harbor seal reactions to acoustic harassment devices (AHDs) with source level of 172 dB deployed around aquaculture sites. Seals were generally unresponsive to sounds from the AHDs. During two specific events, individuals came within 141 and 144 ft (43 and 44 m) of active AHDs and failed to demonstrate any measurable behavioral response; estimated received levels based on the measures given were approximately 120 to 130 dB.
Costa et al. (2003) measured received sound levels from an Acoustic Thermometry of Ocean Climate (ATOC) program sound source off northern California using acoustic data loggers placed on translocated elephant seals. Subjects were captured on land, transported to sea, instrumented with archival acoustic tags, and released such that their transit would lead them near an active ATOC source (at 0.6 mi depth [939 m]; 75-Hz signal with 37.5-Hz bandwidth; 195 dB maximum source level, ramped up from 165 dB over 20 min) on their return to a haul-out site. Received exposure levels of the ATOC source for experimental subjects averaged 128 dB (range 118 to 137) in the 60- to 90-Hz band. None of the instrumented animals terminated dives or radically altered behavior upon exposure, but some statistically significant changes in diving parameters were documented in nine individuals. Translocated northern elephant seals exposed to this particular non-pulse source began to demonstrate subtle behavioral changes at exposure to received levels of approximately 120 to 140 dB.
Several available studies provide information on the reactions of pinnipeds to non-pulsed underwater sound. Kastelein et al. (2006) exposed nine captive harbor seals in an approximately 82 × 98 ft (25 × 30 m) enclosure to non-pulse sounds used in underwater data communication systems (similar to acoustic modems). Test signals were frequency modulated tones, sweeps, and bands of sound with fundamental frequencies between 8 and 16 kHz; 128 to 130 ±3 dB source levels; 1- to 2-s duration (60-80 percent duty cycle); or 100 percent duty cycle. They recorded seal positions and the mean number of individual surfacing behaviors during control periods (no exposure), before exposure, and in 15-min experimental sessions (n = 7 exposures for each sound type). Seals generally swam away from each source at received levels of approximately 107 dB, avoiding it by approximately 16 ft (5 m), although they did not haul out of the water or change surfacing behavior. Seal reactions did not appear to wane over repeated exposure (i.e., there was no obvious habituation), and the colony of seals generally returned to baseline conditions following exposure. The seals were not reinforced with food for remaining in the sound field.
Reactions of harbor seals to the simulated sound of a 2-megawatt wind power generator were measured by Koschinski et al. (2003). Harbor seals surfaced significantly further away from the sound source when it was active and did not approach the sound source as closely. The device used in that study produced sounds in the frequency range of 30 to 800 Hz, with peak source levels of 128 dB at 1 m at the 80- and 160-Hz frequencies.
Ship and boat sound do not seem to have strong effects on seals in the water, but the data are limited. When in the water, seals appear to be much less apprehensive about approaching vessels. Some would approach a vessel out of apparent curiosity, including noisy vessels such as those operating seismic airgun arrays (Moulton and Lawson, 2002). Gray seals (Halichoerus grypus) have been known to approach and follow fishing vessels in an effort to steal catch or the bait from traps. In contrast, seals hauled out on land often are quite responsive to nearby vessels. Terhune (1985) reported that northwest Atlantic harbor seals were extremely vigilant when hauled out and were wary of approaching (but less so passing) boats. Suryan and Harvey (1999) reported that Pacific harbor seals commonly left the shore when powerboat operators approached to observe the seals. Those seals detected a powerboat at a mean distance of 866 ft (264 m), and seals left the haul-out site when boats approached to within 472 ft (144 m).
The studies that address responses of high-frequency cetaceans (such as the harbor porpoise) to non-pulse sounds include data gathered both in the field and the laboratory and related to several different sound sources (of varying similarity to chirps), including: Pingers, AHDs, and various laboratory non-pulse sounds. All of these data were collected from harbor porpoises. Southall et al. (2007) concluded that the existing data indicate that harbor porpoises are likely sensitive to a wide range of anthropogenic sounds at low received levels (around 90 to 120 dB), at least for initial exposures. All recorded exposures above 140 dB induced profound and sustained avoidance behavior in wild harbor porpoises (Southall et al., 2007). Rapid habituation was noted in some but not all studies. Data on behavioral responses of high-frequency cetaceans to multiple pulses is not available. Although individual elements of some non-pulse sources (such as pingers) could be considered pulses, it is believed that some mammalian auditory systems perceive them as non-pulse sounds (Southall et al., 2007).
Southall et al. (2007) also compiled known studies of behavioral responses of marine mammals to airborne sound, noting that studies of pinniped response to airborne pulsed sounds are exceedingly rare. The authors deemed only one study as having quantifiable results. Blackwell et al. (2004) studied the response of ringed seals within 500 m of impact driving of steel pipe pile. Received levels of airborne sound were measured at 93 dB at a distance of 63 m. Seals had either no response or limited response to pile driving. Reactions were described as “indifferent” or “curious.”
Marine mammals are expected to traverse through and not remain in the project area. Therefore, animals are not expected to be exposed to a significant duration of construction sound.
Vessel Operations—A work/equipment barge and small range craft would be present in the Region of Activity at various times due to construction activities. The small range craft vessel would travel at low speeds and would be used to monitor for marine mammals in the area. Such vessels already use the Region of Activity in moderately high numbers; therefore, the vessels to be used in the Region of Activity do not represent a new sound source, only a potential increase in the frequency and duration of these sound source types.
There are very few controlled tests or repeatable observations related to the reactions of marine mammals to vessel noise. However, Richardson et al. (1995) reviewed the literature on reactions of marine mammals to vessels, concluding overall that pinnipeds and many odontocetes showed high tolerance to vessel noise. Mysticetes, too, often show tolerance of slow, quieter vessels. Because the Region of Activity is highly industrialized, it seems likely that marine mammals that transit the Region of Activity are already habituated to vessel noise, thus the additional vessels that would occur as a result of construction activities would likely not have an additional effect on these animals. Vessels occurring as a result of construction activities would be mostly stationary or moving slowly for marine mammal monitoring. Therefore, proposed vessel noise and operations in the Region of Activity is unlikely to rise to the level of harassment.
Physical Disturbance—Vessels and in-water structures have the potential to cause physical disturbance to marine mammals. As previously mentioned, various types of vessels already use the Region of Activity in high numbers. Tug boats and barges are slow moving and follow a predictable course. Marine mammals would be able to easily avoid these vessels while transiting through the Region of Activity and are likely already habituated to the presence of numerous vessels. Therefore, vessel strikes are extremely unlikely and, thus, discountable. Potential encounters would likely be limited to brief, sporadic behavioral disturbance, if any at all. Such disturbances are not likely to result in a risk of Level B harassment of marine mammals transiting the Region of Activity.
Hearing Impairment and Other Physiological Effects
Temporary or permanent hearing impairment is a possibility when marine mammals are exposed to very strong sounds. Non-auditory physiological effects might also occur in marine mammals exposed to strong underwater sound. Possible types of non-auditory physiological effects or injuries that may occur in mammals close to a strong sound source include stress, neurological effects, bubble formation, and other types of organ or tissue damage. It is possible that some marine mammal species (i.e., beaked whales) may be especially susceptible to injury and/or stranding when exposed to strong pulsed sounds, particularly at higher frequencies. Non-auditory physiological effects are not anticipated to occur as a result of proposed construction activities. The following subsections discuss the possibilities of TTS and PTS.
TTS—TTS, reversible hearing loss caused by fatigue of hair cells and supporting structures in the inner ear, 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. TTS can last from minutes or hours to (in cases of strong TTS) days. For sound exposures at or somewhat above the TTS threshold, hearing sensitivity in both terrestrial and marine mammals recovers r