Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Columbia River Crossing Project, Washington and Oregon

Federal RegisterApr 19, 2012

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 217

[Docket No. 110801455-2197-01]

RIN 0648-BB16

Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Columbia River Crossing Project, Washington and Oregon

AGENCY:

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

ACTION:

Proposed rule; request for comments.

SUMMARY:

NMFS has received a request from the Department of Transportation's Federal Transit Authority (FTA) and Federal Highway Administration (FHWA), on behalf of the Columbia River Crossing project (CRC), for authorization to take marine mammals incidental to bridge construction and demolition activities at the Columbia River and North Portland Harbor, Washington and Oregon, over the course of 5 years from approximately July 2013 through June 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.

DATES:

Comments and information must be received no later than May 21, 2012.

ADDRESSES:

You may submit comments on this document, identified by 110801455-2197-01, 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 110801455-2197-01 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 Tammy Adams, Acting 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:

Ben Laws, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Availability

A copy of CRC's application, and other supplemental documents, may be obtained by writing to the address specified above (see

ADDRESSES

), calling the contact listed above (see

FOR FURTHER INFORMATION CONTACT

), or visiting the internet at:

http://www.nmfs.noaa.gov/pr/permits/incidental.htm.

A Draft Environmental Impact Statement (DEIS) on the Columbia River Crossing project, authored by the FTA and FHWA, is available for viewing at

http://www.columbiarivercrossing.org/.

Background

Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361

et seq.

) direct the Secretary of Commerce to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review.

Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s), will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses (where relevant), and if the permissible methods of taking and requirements pertaining to the mitigation, monitoring and reporting of such takings are set forth. NMFS has defined ‘negligible impact’ in 50 CFR 216.103 as “* * * an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.”

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

On November 22, 2010, NMFS received a complete application from CRC requesting authorization for take of three species of marine mammal incidental to construction and demolition activities in the Columbia River and North Portland Harbor, Washington and Oregon. CRC has requested regulations to be effective for the period of 5 years from approximately July 2013 through June 2018; portions of the project that may result in incidental take of marine mammals are anticipated to potentially last until March 2021. Marine mammals would be exposed to various operations, including pile driving and removal, demolition of existing structures, and the presence of construction-related vessels. Because the specified activities have the potential to take marine mammals present within the action area, CRC requests authorization to incidentally take, by Level B harassment only, Steller sea lions (

Eumetopias jubatus

), California sea lions (

Zalophus californianus

), and harbor seals (

Phoca vitulina

Description of the Specified Activity

CRC is proposing a multimodal transportation project along a 5-mile section of the Interstate 5 (I-5) corridor connecting Vancouver, Washington, and Portland, Oregon. There are significant

congestion, safety, and mobility problems in the CRC project area. The existing northbound bridge was built in 1917, and the southbound bridge was added in 1958. These bridges have been classified as functionally obsolete because they do not meet current or future demands for interstate service, resulting in congestion-related delays. Assuming that no changes are made, the daily congestion period is projected to grow from the current 6 hours to 15 hours by 2030 (CRC, 2008). In addition, this section of I-5 has an accident rate more than double that of similar urban highways. Narrow lanes, short on-ramps, and non-standard shoulders on the bridges contribute to accidents. When bridge lifts occur to allow passage of river traffic, all vehicular traffic is stopped, resulting in delays on connecting roadways and adding to unsafe driving conditions.

Current public transit service between Vancouver and Portland is limited to bus service constrained by the limited capacity in the I-5 corridor and is subject to the same congestion as other vehicles, which affects transit reliability and operations. Bicycle and pedestrian facilities are currently substandard in much of the project area.

Seismic safety is also an important issue. Recent geotechnical studies have shown that the sandy soil under the mainstem Columbia River bridges would likely liquefy to a depth of 85 ft (26 m) during an earthquake greater than magnitude 8.0. This could cause irreparable damage to the bridges and potential loss of human life.

To remedy these deficiencies, the CRC project proposes:

• Replacement of the existing Columbia River bridges with two new structures;

• Widening of the existing North Portland Harbor Bridge, and construction of three new structures across the harbor; and

• Demolition of existing Columbia River bridges.

The new Columbia River crossing would carry traffic on two separate pier-supported bridges and would include a new light rail transit (LRT) line and improved bicycle/pedestrian facilities, using a stacked alignment that would reduce the number of in-water piers in the Columbia River by approximately one-third from alternative designs. CRC proposes six in-water pier complexes for a total of twelve piers for the Columbia River bridges.

CRC proposes to widen the existing I-5 southbound bridge over North Portland Harbor, and would add three new bridges adjacent to the existing bridges. From east to west, these structures would carry:

• A three-lane northbound collector-distributor (CD) ramp carrying local traffic;

• Northbound and southbound I-5 on the widened existing bridge across the North Portland Harbor;

• Southbound CD ramps carrying local traffic; and

• LRT combined with a bicycle/pedestrian path.

Each bridge would have four or five in-water bents, consisting of one to three drilled shafts. A bent is part of a bridge's substructure, composed of a rigid frame commonly made of reinforced concrete or steel that supports a vertical load and is placed transverse to the length of a structure. Bents are commonly used to support beams and girders. Each vertical member of a bent may be called a column, pier or pile. The horizontal member resting on top of the columns is a bent cap. The columns stand on top of some type of foundation or footer that is usually hidden below grade. A bent commonly has at least two or more vertical supports.

The permanent in-water piers of both the Columbia River and North Portland Harbor crossings would be constructed using drilled shafts, rather than impact-driven piles. However, the project would require numerous temporary in-water structures to support equipment and materials during the course of construction, which may require the use of temporary impact-driven piles. These structures would include work platforms, work bridges, and tower cranes. Project construction would require the installation and removal of approximately 1,500 temporary steel piles.

The existing Columbia River bridges would be demolished after the new Columbia River bridges have been constructed and after associated interchanges are operating. The existing Columbia River bridges would be demolished in two stages: (1) Superstructure demolition and (2) substructure demolition. In-water demolition would be accomplished either within cofferdams or with the use of diamond wire/wire saw. A full description of the activities proposed by CRC is described in the following sections.

Region of Activity

The Region of Activity is located within the Lower Columbia River sub-basin. The Columbia River and its tributaries are the dominant aquatic system in the Pacific Northwest. The Columbia River originates on the west slope of the Rocky Mountains in Canada and flows approximately 1,200 mi (1,931 km) to the Pacific Ocean, draining an area of approximately 219,000 mi

(567,207 km

) in Washington, Oregon, Idaho, Montana, Wyoming, Nevada, and Utah. Saltwater intrusion from the Pacific Ocean extends approximately 23 mi (37 km) upstream from the river mouth at Astoria, Oregon. Coastal tides influence the flow rate and river level up to Bonneville Dam at river mile (RM) 146 (RKm 235) (USACE, 1989).

The project area is highly altered by human disturbance, and urbanization extends to the shoreline. There has been extensive removal of streamside forests and wetlands. Riparian areas have been further degraded by construction of dikes and levees and the placement of stream bank armoring. For several decades, industrial, residential, and upstream agricultural sources have contributed to water quality degradation in the river. Additionally, existing levels of disturbance are high due to heavy commercial shipping traffic.

The I-5 bridges are located at RM 106 (RKm 171) of the Columbia River. From north to south, the I-5 bridges cross the Columbia River from Vancouver, Washington, to Hayden Island in Portland, Oregon. From Hayden Island, a single I-5 bridge crosses North Portland Harbor to the mainland in Portland, Oregon. The North Portland Harbor is a large side channel of the Columbia River that flows between the southern bank of Hayden Island and the Oregon mainland. The channel branches off the Columbia River approximately 2 RM (3 RKm) upstream (east) of the existing bridge site, and flows approximately 5 RM (8 RKm) downstream (west) before rejoining the mainstem Columbia River (please see Figure 2-2 of CRC's application). The Region of Activity has been defined as the area of the Columbia River and North Portland Harbor in which marine mammals may be directly impacted by sound generated by in-water construction activities, i.e., the area in which modeling indicates that underwater sound generated by the project would be greater than 120 dB re: 1 μPa root mean square (rms; all underwater sound discussed in this document is referenced to 1 μPa).

Due to the curvature of the river and islands present, underwater sound from pile installation would encounter land before it reaches modeled distances to the 120 dB disturbance threshold. Sound from pile installation could not extend beyond Sauvie Island, approximately 5.5 RM (8.9 RKm) downstream, and Lady Island, 12.5 RM (20 RKm) upstream; thus, this distance

represents the extent of the Region of Activity downstream and upstream of CRC project construction activities. This distance encompasses the Columbia River from approximately RM 101 to 118 (RKm 163 to 190). Within North Portland Harbor, the maximum distance that underwater sound could extend would be 3.5 mi (5.6 km) downstream and 1.9 mi (3.1 km) upstream of CRC project construction activities.

Dates of Activity

CRC has requested regulations governing the incidental take of marine mammals for the 5-year period from July 2013 through June 2018. Construction activities for both the Columbia River and North Portland Harbor bridges are estimated to begin in July 2013. Construction activities for the Columbia River bridges are estimated to end in 2017, while construction activities for the North Portland Harbor bridges are estimated to end in 2016. Demolition of the existing Columbia River bridges is expected to occur for eighteen months, from approximately September 2019 until March 2021. However, some demolition could possibly occur during the proposed 5-year authorization period. Table 1 provides an overview of the anticipated CRC project timeline and sequencing of project elements. Funding would be a significant factor in determining the overall sequencing and construction duration. Contractor schedules, weather, materials, and equipment could also influence construction duration. CRC would seek additional authorization under the MMPA for any in-water work continuing beyond the expiration of the proposed rule.

The existing in-water work window for this portion of the Columbia River and North Portland Harbor, developed to reduce construction impacts to Endangered Species Act (ESA)-listed fish species, is November 1 through February 28. Because of the large amount of in-water work required, the CRC project would not be able to complete the in-water work during this time period. Therefore, CRC has requested a variance to the in-water work window established by the Oregon and Washington Departments of Fish and Wildlife (ODFW and WDFW, respectively). Most in-water construction activities are proposed to occur year-round, although impact pile driving would occur only from September 15 to April 15. The rationale for CRC's proposed variance takes into account project hydroacoustic impacts in relation to run timing for ESA-listed fish species. The project's timing for impact pile driving overlaps with pinniped presence (primarily January through May) from approximately January through April 15.

Table 1—Proposed Timing of In-Water Work

[CR = Columbia River; NPH = North Portland Harbor]

Activity

Description

Activity duration

Timing

1. Install small-diameter piles (less than or equal to 48 in (1.2 m)) with impact methods

Small-diameter piles would be used in the construction of temporary work bridges/platforms, tower cranes, and support platforms

45 min/day (impact hammer operation) with up to 7.5 min/week of unattenuated driving in CR and 5 min/week of unattenuated driving in NPH

138 days in CR, 134 days in NPH

Only within approved extended in-water work window of September 15 through April 15 each year.

2. Install small-diameter piles with non-impact methods

Small-diameter piles would be used in the construction of temporary work bridges/platforms, barge moorings, tower cranes, and oscillator support platforms

Length of work day is subject to local sound ordinances, however could be up to 24 hours/day

138 days in CR, 134 days in NPH

Year-round provided work does not violate water quality standards.

3. Extract small-diameter piles (not including cofferdams)

Removal of small-diameter piles would be done using vibratory equipment or direct pull

Length of work day is subject to local sound ordinances, however could be up to 24 hours/day

Year-round provided work does not violate water quality standards.

4. Install/remove cofferdam for construction of Columbia River bridges

Used to construct piers nearest to shore in the Columbia River (Pier complexes 2 and 7). Steel sheet pile sections to be installed by non-impact means to form a cofferdam. Sheet pile removal can be direct pull or use a vibratory hammer

Cofferdams could be in place for a maximum of 250 work days each. Installation and dewatering of each cofferdam would not take more than 65 work days; cofferdam removal would not take more than 25 work days. Length of work day is subject to local sound ordinances

Year-round provided work does not violate water quality standards.

5a. Install large-diameter drilled shaft casings (greater than or equal to 72 in (1.8 m)) using vibratory hammer, rotator, or oscillator outside of a cofferdam

Used to construct piers and bents not immediately adjacent to shore in the Columbia River and North Portland Harbor

CR: 110-120 days/pier complex

NPH: approximately 8 days/shaft.

Year-round provided work does not violate water quality standards.

5b. Install large-diameter drilled shaft casings using vibratory hammer, rotator, or oscillator inside of a water- or sand-filled cofferdam

Used to construct piers and bents nearest to shore in the Columbia River and North Portland Harbor

CR pier complexes 2 and 7: approximately 84 days each

NPH: approximately 8 days/shaft.

Year-round provided work does not violate water quality standards.

6. Clean out shafts and place reinforcing and concrete inside steel casings

Applies to all piers and shafts. All activities/materials would be contained within the casings and have no contact with the water

CR: 110-120 days/pier complex

NPH: approximately 8 days/shaft.

Year-round provided work does not violate water quality standards.

7a. Perform placement of reinforcement and concrete for a cast-in-place pile cap

Possible construction method for shaft cap at pier complexes 2 and 7. All activities and materials would be contained within forms and would have no contact with the water. The bottom of the pier caps may sit below the mud line

Estimate 95 work days per pier

Year-round. For pier caps nearest shore: year-round if work occurs within a de-watered cofferdam.

7b. Place a prefabricated pile cap, form, pile template, or similar element into the water

At CR pier complexes 3-6. Potentially at pier complexes 2 and 7. Assume contact with the water surface, but not with the riverbed

100 work days per pier

For deep water piers: year-round provided work does not violate water quality standards. For piers nearest shore: year-round if work occurs within a de-watered cofferdam.

8. Install and remove cofferdam for demolition of existing Columbia River bridges

Steel sheet pile sections would be installed with a vibratory hammer or pushed in, to form a cofferdam. Sheet pile removal can be direct pull or with a vibratory hammer. More than one cofferdam is to be in use at a time

Approximately 370 days

Installation: 10 work days per pier, Demolition: 20 work days per pier, Removal: 10 work days per pier.

Year-round provided work does not violate water quality standards.

9a. Perform wire saw/diamond wire cutting outside of a cofferdam at or below the water surface

Used throughout for demolition of existing bridges to cut concrete piers into manageable pieces. These pieces would then be loaded onto barges and transported off site

Pier cutting and removal to take approximately 7 work days per pier

Year-round provided work does not violate water quality standards.

9b. Perform wire saw/diamond wire cutting or a hydraulic breaker inside of a cofferdam

Used for demolition of the existing Columbia River bridges. Used in water to cut concrete piers into manageable pieces. Cofferdam would not be dewatered

Pier cutting and removal to take approximately 7 work days per pier

Year-round provided work does not violate water quality standards.

10. Remove material from river bed

Old pier/bent foundations or riprap from North Portland Crossing would be removed if obstructing construction. Would use bucket dredge

Less than 7 work days during the published standard in-water work window per pier

No variance requested. November 1 to February 28.

10a. Spot remove debris and riprap from river bed

Guided removal (likely underwater diver assisted) of specific pieces of debris or large riprap only in the location where the shaft would be drilled. In North Portland Harbor only. Would use bucket dredge

Up to 2 hrs/day. Less than 7 work days

Year-round provided work does not violate water quality standards.

Note:

Proposed timing is contingent upon obtaining an in-water work variance from all relevant regulatory agencies.

To reduce number of impact pile strikes, temporary piles that are load-bearing would be vibrated to refusal, then driven and proofed with an impact hammer to confirm load-bearing capacity.

In the event water quality monitoring determines that work exceeds water quality standards, all in-water work would be suspended until corrective measures can be implemented.

Description of the Activity—Columbia River Bridges

The project would construct two new bridges across the Columbia River downstream (to the west) of the existing interstate bridges. Each of the structures would range from approximately 91 to 136 ft (28-41 m) wide, with a gap of approximately 15 ft (5 m) between them. The over-water length of each new mainstem bridge would be approximately 2,700 ft (823 m).

The Columbia River bridges would consist of six in-water pier complexes of two piers each, for a total of twelve in-water piers. Piers 3-6 would each have separate structures for the northbound and southbound bridges. Each pier would consist of up to nine 10-ft-diameter (3 m) drilled shafts topped by a shaft cap (see Figure 1-4 of CRC's application for illustration). Pier complexes 2 through 7 are in-water, beginning on the Oregon side. Pier complex 1 would be on land in Oregon, while pier complex 8 would be on land in Washington. Portions of pier complex 7 occur in shallow water (less than 20 ft [6 m] deep). The basic configuration of these bridges, the span lengths, and the layout of the bridges relative to the Columbia River shoreline and navigation channels are illustrated in Figure 1-2 of CRC's application.

The proposed Columbia River mainstem crossing design uses dual stacked bridge structures, which reduces the number of in-water piers in the Columbia River by approximately one-third compared with alternative designs, and greatly reduces both the temporary construction impacts and the permanent effects of in-water piers. The western structure would carry southbound I-5 traffic on the top deck,

with LRT on the lower deck. The eastern structure would carry northbound I-5 traffic on the top deck, with bicycle/pedestrian traffic on the lower deck.

At each pier complex, sequencing would occur as listed below. Details of each activity are presented in following sections.

• Install temporary cofferdam (applies to pier complexes 2 and 7 only).

• Install temporary piles to moor barges and to support temporary work platforms (at pier complexes 3 through 6) and work bridges (at pier complexes 2 and 7).

• Install drilled shafts for each pier complex.

• Remove work platform or work bridge and associated piles.

• Install shaft caps at the water level.

• Remove cofferdam (applies to pier complexes 2 and 7 only).

• Erect tower crane.

• Construct columns on the shaft caps.

• Build bridge superstructure spanning the columns.

• Remove tower crane.

• Connect superstructure spans with mid-span closures.

• Remove barge moorings.

A construction sequence was developed for building the new Columbia River bridges and demolishing the existing structures (see Figure 1-5 of CRC's application). Once a construction contract is awarded, the contractor may sequence the construction in a way that may not conform exactly to the proposed schedule but that best utilizes the materials, equipment, and personnel available to perform the work. However, the amount of in-water work that can be conducted at any one time is limited, and is based on three factors:

1. The amount of equipment available to build the project would likely be limited. Based on equipment availability, the CRC engineering team estimates that only two drilled shaft operations could occur at any time.

2. The physical space the equipment requires at each pier would be substantial. The estimated sizes of the work platforms/bridges and associated barges are shown in Appendix A of CRC's application. This is a conceptual design developed by the CRC project team to provide a maximum area of impact. The actual work platforms would be designed by the contractor; therefore, actual sizes would be determined at a later date. The overlap of work platforms/bridges and barge space limits the amount and type of equipment that can operate at a pier complex at one time.

3. The U.S. Coast Guard has required that one navigation channel be open at all times during construction, to the extent feasible.

All the activities listed above may occur at more than one pier complex at a time. Please see Appendix A of CRC's application for conceptual diagrams of the construction sequence.

Temporary Structures

—Pier complexes 2 and 7 would each require one temporary cofferdam. Cofferdams would consist of interlocking sections of sheet piles to be installed with a vibratory hammer or with press-in methods. Cofferdams would be removed using a vibratory hammer or direct pull.

Additionally, the project would include numerous temporary in-water structures to support equipment and materials during the course of construction. These structures would include work platforms, work bridges, and tower cranes. They would be designed by the contractor after a contract is awarded, but prior to construction.

Work platforms, which would surround the future location of each shaft cap, would be constructed at pier complexes 3 through 6. A conceptual design of a temporary in-water work platform may be found in CRC's application (Figure 11 of Appendix A). Work bridges would be installed at pier complexes 2 and 7 so that equipment can access these pier complexes directly from land. Temporary work bridges would be placed only on the landward side of these pier complexes. The bottom of the temporary work platforms and bridges would be a few feet above the water surface. The decks of the temporary work structures would be constructed of large, untreated wood beams to accommodate large equipment, such as 250-ton cranes. After drilled shafts and shaft caps have been constructed, the temporary work platforms and their support piles would be removed.

After work platforms/bridges are removed at a given pier complex, one tower crane would be constructed between each pair of adjacent piers that makes up the pier complex. The crane would construct the bridge columns and the superstructure. Following construction of the columns and superstructure, the tower cranes and their support piles would be removed.

Steel pipe piles would be used to support the temporary support structures. In addition, four temporary piles could surround each of the drilled shafts. Due to the heavy equipment and stresses placed on the support structures, all of these temporary piles would need to be load-bearing. Load-bearing piles would be installed using a vibratory hammer and then proofed with an impact hammer to ensure that they meet project specifications demonstrating load-bearing capacity. The number and size of temporary piles for these structures is listed in Table 2.

Table 2—Summary of Steel Pipe Piles and Temporary Structures Required for Construction of Columbia River Bridges

Structure

Number

Pile diameter

Pile length

Piles per structure

Total number of piles

Duration present in water (days-each)

Work platforms/bridges

18-24 in (0.5-0.6 m)

70-90 ft (21-27 m)

100

600

260-315.

42-48 in (1.1-1.2 m)

120 ft (37 m)

192

Tower cranes

42-48 in

120 ft

150-275.

Barge moorings

N/A

18-24 in

70-90 ft

Varies

120/mooring.

Barges (cumulative, at a single time)

Up to 12

N/A

Varies.

Total

Varies

920

Barges would be used as platforms to conduct work activities and to haul materials and equipment to and from the work site. Barges would be moored to non-load-bearing steel pipe piles and adjacent to temporary work structures. Several types and sizes of barges would be used for bridge construction. The type and size of a barge would depend on how the barge is used. No more than twelve barges are estimated to be moored or active in the Columbia River at any one time throughout the construction period. Barges would be moored around each pier complex. Approximately eighty mooring piles would be installed over the life of the project, each in place for approximately 120 work days. Mooring piles would be vibrated into the sediment until refusal. Vibratory installation would take between 5-30 minutes per pile.

The number of temporary platforms or bridges in the Columbia River at one time would vary between zero and three during construction. Up to four work platforms and two work bridges would be required to install drilled shafts and construct shaft caps. Each work platform/bridge would require 22 to 25 work days to install. Each work platform/bridge would be in place for approximately 260 to 315 work days. Each tower crane would require approximately two work days to drive support piles and an additional thirteen work days to construct the platform. Each tower crane would be in place for approximately 150 to 275 work days.

Load-bearing piles (used for work platforms/bridges and tower cranes) would be vibrated to refusal (approximately 5-30 minutes per pile), then driven and proofed with an impact hammer to confirm load-bearing capacity. An average of six temporary piles would be installed per day using vibratory installation to set the piles, and up to two impact drivers to proof them. Rates of installation would be determined by the type of installation equipment, substrate, and required load-bearing capacity of each pile. Temporary piles would be installed and removed throughout the construction process. No more than two impact pile drivers would operate at one time. Use of two impact pile drivers would primarily occur within a single pier complex.

In general, temporary piles would extend only into the alluvium to an approximate depth of 70 to 120 ft (21-37 m). Standard pipe lengths are 80 to 90 ft (24-27 m), so some piles may need to be spliced to achieve these depths.

Estimated pile installation specifications are provided in Table 3. The number of pile strikes was estimated by Washington Department of Transportation (WSDOT) geotechnical and CRC project engineers, based on information from past projects and knowledge of site sediment conditions. The actual number of pile strikes would vary depending on the type of hammer, the hammer energy used, and substrate composition. The strike interval of 1.5 seconds (forty strikes per minute) is also estimated from past projects and is based on use of a diesel hammer. This estimate is within the typical range of 35-52 strikes per minute for diesel hammers (HammerSteel, 2009). As shown in Table 3, for any one 12-hour daily pile driving period, less than 1 hour of pile driving would occur. Please see Table 8 for a summary of time required for vibratory driving.

Table 3—Pile Strike Summary for Construction in Columbia River

Pile Size

Estimated piles

installed per day

Estimated strikes per pile

Estimated

maximum strikes per day

Hours of pile

driving per 12-hr

daily pile driving

work period*

18-24 in (0.5-0.6 m)

300

600

0.25

42-48 in (1.1-1.2 m)

300

1,200

0.50

Total

N/A

1,800

0.75

* This scenario assumes just one pile being driven at a time. During construction, up to two piles may be driven at the same time in the Columbia River. If this were to occur, the strike numbers would stay the same, but the actual driving time would decrease.

A sound attenuation device (

i.e.,

bubble curtain) would be used during all impact pile driving, with the exception of periods when the device would be turned off to measure its effectiveness, in accordance with the hydroacoustic monitoring plan. A period of up to 7.5 min per week of pile driving without the use of an attenuation device has been allocated in analyses of project impacts, to allow for this study of mitigation effectiveness, as well as for instances when the device might fail. If the attenuation device fails, pile driving activities would shut down as soon as practicable and resolution of the problem would occur; however, some amount of unattenuated driving may occur before shut-down can safely occur. By incorporating this time into the analysis, the project may still proceed in the event of an equipment failure without exceeding analyzed thresholds. With the exception of hydroacoustic monitoring, intentional impact pile driving without a sound attenuation device is not proposed nor would it be authorized. In addition, to limit hydroacoustic impacts to marine mammals, there would be, at minimum, a consecutive 12-hour period without impact pile driving for every 24-hour day.

Permanent Structures

—In-water drilled shaft construction is accomplished by installing large diameter steel casing to a specified depth (up to −270 ft (−82 m) North American Vertical Datum of 1988) to the top of the competent geological layer, which is the Troutdale Formation in the project area. The top layer of river substrate is composed of loose to very dense alluvium (primarily sand and some fines), beneath which is approximately 20 ft (6 m) of dense gravel, underlain by the Troutdale Formation.

A vibratory hammer, oscillator, or rotator would be used to advance a casing. If casings are installed by a vibratory hammer, installation is estimated to be 1 work day per casing. If casings need to be welded together, 1 work day is estimated for the weld. No more than two casings are estimated per shaft. Soil would be removed from inside the casing and transferred onto a barge as the casing is advanced, and the soil would be deposited at an approved upland site. Drilling would continue below the casing approximately 30 ft (9 m) into the Troutdale Formation to a specified tip elevation. After excavating soil from inside the casing, reinforcing steel would be installed into the shaft and then the shaft would be filled with concrete.

During construction of the drilled shafts, uncured concrete would be poured into water-filled steel casings, creating a mix of concrete and water. As

the concrete is poured into the casing, it would displace this highly alkaline mixture. The project would implement best management practices (BMPs) to contain the mixture and ensure that it does not enter any surface water body. Once contained, the water would be treated to meet state water quality standards and either released to a wastewater treatment facility or discharged to a surface water body. The steel casing may or may not be removed, depending on the installation method. Figures 1-6 through 1-9 of CRC's application depict typical drilled shaft operations and equipment.

The total duration of the permanent shaft installation could vary considerably depending on the type of installation equipment used, the quantity of available installation equipment, and actual soil conditions. Installation of each drilled shaft is estimated to take approximately 10 days. With the limited in-water work window for impact pile driving and construction phasing constraints, the total duration of drilled shaft installation would be approximately thirty months. For each of the in-water pier complexes (Piers 2-7), six to nine shafts would be drilled. For piers 3-6, which would support separate northbound and southbound bridges, this means a minimum of 48 drilled shafts. For piers 2 and 7, which would support a unified structure, there would be a minimum of twelve drilled shafts. At minimum, there would be an overall total of 72 drilled shafts.

Precast shaft caps would be placed on top of the drilled shafts. Installation of the shaft caps would require cranes, work barges, and material barges. Columns would be constructed of cast-in-place reinforced concrete or precast concrete. Column construction is estimated to take 120 days for each pier complex. Construction of columns would require cranes, work barges, and material barges in the river year-round. The superstructure would be constructed of structural steel, cast-in-place concrete, or precast concrete. Precast elements would be fabricated at a casting yard.

Description of the Activity—North Portland Harbor Bridges

The existing North Portland Harbor bridge would be upgraded to meet current seismic standards. The seismic retrofit activities would consist solely of minor modifications to the bent caps and girders that would not require in-water work. In addition, four new bridge structures would be constructed across North Portland Harbor. The bridges, illustrated in Figure 1-12 of CRC's application are, from west to east: the LRT/pedestrian/bicycle bridge, I-5 southbound off-ramp, I-5 southbound on-ramp, existing mainline, and I-5 northbound on-ramp.

The existing North Portland Harbor bridge was constructed in the early 1980s of prestressed concrete girders and reinforced concrete bents. The bents are supported by driven steel pilings. Two previous bridges, constructed in 1917 and 1958, were built at the same location as the current bridge, but may not have been fully removed during subsequent replacement efforts. These bridges had reinforced concrete bents supported on timber piles. Some of this material may still be present, but this would not be confirmed until construction begins. Some removal of previous bridge elements is anticipated prior to installation of the new bridge shafts. Removal of remnant bridge elements would be with a clamshell dredge. The five new or improved bridges over the North Portland Harbor would range from approximately 900-1,000 ft (274-305 m) over water, and would range from 40-150 ft (12-46 m) in width. Bridge widths would vary due to merging of lanes on some structures.

Construction is expected to be sequential, beginning with either of the most nearshore bents of a given bridge and proceeding to the adjacent bent. The actual sequencing would be determined by the contractor once a construction contract is awarded. No more than three of the five bridges are likely to have in-water work occurring simultaneously. For the bents closest to shore, construction would occur from work bridges. At the other in-water bents, as described for Columbia River bridges, construction would likely occur from barges and support platforms. General construction activities to build the bents and superstructure are similar to those for the Columbia River bridges, except that shaft caps would not be used and bridge decks would be placed on girders instead of balanced cantilevers. General sequencing of the construction of a single bridge appears below. Some of these activities may occur simultaneously at separate bents.

• Construct support platforms and work bridges using vibratory and impact pile drivers.

• Vibrate temporary piles for barge moorings.

• Extract large pieces of debris as needed to allow casings to advance.

• Install drilled shafts at each bent.

• Construct columns on the drilled shafts.

• Construct a bent cap or crossbeam on top of the columns at a bent location.

• Erect bridge girders on the bent caps or crossbeams.

• Place the bridge deck on the girders.

• Remove temporary work bridges, support platforms, and supporting piles.

Temporary Structures

—At the bents closest to shore, up to nine temporary work bridges would be constructed to support equipment for drilled shafts. In addition, at each of the 31 bent locations, one support platform would be constructed, each consisting of four load-bearing piles. The bridges and support platforms would be designed by the contractor after a contract is awarded, but prior to construction. The number and size of piles for temporary in-water work structures are listed in Table 4.

Table 4—Approximate Number of Steel Pipe Piles Required for Construction of North Portland Harbor Bridges

Structure

Number

Pile diameter

Pile length

Piles per structure

Total number of piles

Duration present in water

(days-each)

Work bridges

18-24 in (0.5-0.6 m)

70-120 ft (21-37 m)

225

20-42.

Support platforms

36-48 in (0.9-1.2 m)

120 ft

124

10-34.

Barge moorings

N/A

36-48 in

120 ft

N/A

216

30/mooring.

Barges (cumulative, at a single time)

Up to 9

N/A

10-34.

Total

Varies

565

As with the mainstem Columbia River bridges, temporary piles would be required to support in-water work bridges or to moor barges during construction of the North Portland Harbor bridges. Unlike the Columbia River bridges, cofferdams are not necessary. Piles used for the temporary work bridges and the support platforms must be load bearing. They would first be vibrated to refusal, and then proofed with an impact hammer to confirm load-bearing capacity. An average of three load-bearing piles would be installed per day using vibratory installation to set the piles, with one impact driver to proof. Rates of installation would be determined by the type of installation equipment, substrate, and required load-bearing capacity of each pile.

Temporary mooring piles would be installed and removed throughout the construction process. Installation of these mooring piles could occur year-round and at any time during sufficient visibility. These piles would be installed using vibratory methods only. In general, temporary piles would extend only into the alluvium to an estimated depth of 70 to 120 ft (21-37 m). Standard pipe lengths are 80 to 90 ft (24-27 m), so some piles may need to be welded to achieve the lengths required to drive them to these depths. Estimated pile installation specifications are provided in Table 5. Estimates of required number of strikes per pile and total strikes are the same as for the Columbia River. However, only one impact driver at a time would be used. Impact pile driving is proposed to occur only during a modified in-water work period from approximately September 15 to April 15. No impact pile driving would occur outside of the approved dates.

As discussed for Columbia River, a sound attenuation device (i.e., bubble curtain) would be used during all impact pile driving, with the exception of periods when the device would be turned off to measure its effectiveness, in accordance with the hydroacoustic monitoring plan. A period of up to 5 minutes per week of pile driving without the use of an attenuation device has been allocated in analyses of project impacts for North Portland Harbor, to allow for this study of mitigation effectiveness, as well as for instances when the device might fail. If the attenuation device fails, pile driving activities would shut down as soon as practicable and resolution of the problem would occur; however, some amount of unattenuated driving may occur before shut-down can safely occur. By incorporating this time into the analysis, the project may still proceed in the event of an equipment failure without exceeding analyzed thresholds. With the exception of hydroacoustic monitoring, intentional impact pile driving without a sound attenuation device is not proposed nor would it be authorized. In addition, to limit hydroacoustic impacts to marine mammals, there would be, at minimum, a consecutive 12-hour period without impact pile driving for every 24-hour day. Please see Table 8 for a summary of time required for vibratory driving.

Table 5—Pile Strike Summary for Construction in North Portland Harbor

Pile size

Estimated piles

installed per day

Estimated strikes per pile

Estimated

maximum strikes per day

Hours of pile

driving per 12-hr daily pile driving work period

18-24 in (0.5-0.6 m)

300

900

0.375

36-48 in (0.9-1.2 m)

300

900

0.375

Total

N/A

1,800

0.75

Barges would be used as platforms for conducting work activities and to haul materials and equipment to and from the work site. Barges would be moored with steel pipe piles adjacent to temporary work bridges or bents. Several types and sizes of barges would be used according to specific function. No more than nine barges are estimated to be present in North Portland Harbor at any one time during the construction period.

Following installation of the drilled shafts, the temporary work structures and their support piles would be removed through vibratory methods. Other temporary piles would be installed to moor barges adjacent to the new bents. These non-load bearing piles would be installed through vibratory methods only. The installation of steel pipe piles would occur throughout the construction period. Steel piles would be installed and removed during the multi-year construction of the temporary support structures. Although the project would use over 500 piles in the North Portland Harbor, only 100 to 200 piles are estimated to be in the water at any one time.

Debris Removal

—Debris from previous structures, including foundations from the 1917 and 1953 bridges, may be present in North Portland Harbor at some locations where drilled shafts would be installed. This debris is likely to consist of large rock or old concrete. Because casings cannot advance through this type of material, it must be removed. Removal would consist of capturing the debris in a clamshell bucket. Capture of sediment would be limited. Debris would be placed in an upland location, and disposed of at a landfill if appropriate. Debris removal activities would be limited to the designated in-water work window of November 1 through February 28. Removal activities would take no more than 10 days over the course of construction.

Before debris removal begins, divers would pinpoint the location of the material. Debris removal would only occur in the precise locations where material overlaps with the footprint of the new shafts, greatly minimizing the areal extent of the activity. The amount of material in this location is unknown; however, assuming a worst-case scenario (that the area of the material is the same as the footprint of the drilled shafts), the project would remove debris in no more than 31 locations over an area of roughly 2,433 ft

(226 m

). No more than 90 yd

(69 m

) of material would be removed. If any items are found during excavation that contain potential contaminants (e.g., buried drums, car bodies containing petroleum products), activities to control and clean up contaminants would be implemented in accordance with the project's approved Spill Prevention, Control, and Countermeasures (SPCC) plan.

Permanent Structures

—In-water drilled shaft construction for the North Portland Harbor would occur as described for the Columbia River bridges. Installation of each drilled shaft is estimated to take approximately 10 days. However, the total duration of this activity could vary considerably depending on the type of equipment

used, the quantity of available equipment, and on-site soil conditions. The total duration of drilled shaft installation would be approximately eighteen months. A maximum of 31 shafts would be installed for the North Portland Harbor bridges. Each bridge would have four to seven spans, each a maximum of 255 ft (78 m) long. Each new bridge would have three to five in-water bents, consisting of one to three 10-ft diameter (3 m) drilled shafts. Unlike the Columbia River piers, shafts would not be topped by a shaft cap. Current designs place all of the bents in shallow water (less than 20 ft (6 m) deep).

Columns would be constructed of cast-in-place reinforced concrete. Construction of cast-in-place columns would require cranes, work barges, and material barges continuously throughout this period. The superstructure would consist of girders and a deck. Girders would be constructed of structural steel, cast-in-place concrete, or precast concrete. Precast girders may be fabricated at a casting yard. A cast-in-place concrete deck would be placed on the girders.

Description of the Activity—Columbia River Bridge Demolition

Demolition of the superstructure would begin with removal of the counterweights. The lift span would be locked into place and the counterweights would be cut into pieces and transferred off-site via truck or barge. Next, the lift towers would be cut into manageable pieces and loaded onto barges by a crane. Prior to removal of the trusses, the deck would be removed by cutting it into manageable pieces; these pieces would be transported by barge or truck or by using a breaker, in which case debris would be caught on a barge or other containment system below the work area. After demolition of the concrete deck, trusses would be lifted off of their bearings and onto barges and transferred to a shoreline dismantling site.

The existing Columbia River bridge structures comprise eleven pairs of steel through-truss spans with reinforced concrete decks, including one pair of movable spans over the primary navigation channel and one pair of 531-ft long (162 m) span trusses. The remaining nine pairs of trusses range from 265 to 275 ft (81-84 m) in length. In addition to the trusses, there are reinforced concrete approach spans (over land) on either end of the bridges.

Nine sets of the eleven existing Columbia River bridge piers are below the ordinary high water (OHW) level and are supported on a total of approximately 1,800 driven timber piles. Demolition methods are not finalized; however, the final design would consider factors such as pier depth, safety, phasing constraints, and impacts to aquatic species. Demolition of the concrete piers and timber piling foundations would be accomplished using one of two methods:

1. After removal of the trusses, a cofferdam would be installed at each of the nine in-water bridge piers to contain demolition activities. Cofferdams would not be dewatered. The piers would be broken up and removed from within the cofferdam. Timber piles that pose a navigation hazard would then be extracted or cut off below the mud line.

2. A diamond wire/wire saw would be used to cut the piers into manageable chunks that would be transported offsite. Cofferdams would not be used. Timber piles would then be extracted or cut off below the mud line. With either method, the pieces of the piers would be removed via barge.

Although maintenance personnel regularly inspect the existing bridge, the timber piles located underneath the existing piers are inaccessible and have not been inspected. Therefore, it is unknown whether these timber piles have been treated with creosote, but given their age and intended purpose, it is assumed that they have been so treated. Only piles that could pose a navigation hazard would be removed or cut off below the mud line. These piles include those that are present in the proposed navigation channels and any that extend above the surface of the river bed. Piles would be removed (using a vibratory extractor, direct pull, or clam shell dredge) or cut off below the mud line using an underwater saw. The exact number of piles to be removed is unknown.

A conceptual demolition sequence was determined based on the amount of equipment likely available to build the project and the physical space the equipment requires at each pier. The sequence is provided in Appendix A, Figures 12-16 of CRC's application. The actual construction sequence would be determined by the contractor once a construction contract is awarded. Demolition would occur after the new Columbia River replacement bridges are built. Demolition activities would take approximately eighteen months, from approximately September 2019 until March 2021. However, some demolition activities could occur during the period of this proposed rule.

Temporary Structures

—Temporary cofferdams would be required to isolate work activities and temporary piles would be installed to anchor work and material barges during demolition of the spans and in-water piers. If the diamond wire/wire saw is not used, a temporary cofferdam consisting of interlocking sections of sheet piles would be used to isolate demolition activities at each of the nine in-water piers. Sheet piles for cofferdams would be installed with a vibratory hammer or a press-in method. Up to three cofferdams would be in place at any given time. Sheet piles would be removed using a vibratory hammer or direct pull.

Barges would be used as platforms to perform the demolition and to haul materials and equipment to and from the work site. Several types and sizes of barges are anticipated to be used for bridge demolition. The type and size of each barge would depend on how the barge is used. Up to six stationary or moving barges are expected to be present at any one time during bridge demolition. Over 300 steel pipe piles would be used to anchor and support the work and material barges necessary for demolition. Table 6 summarizes temporary pile use during bridge demolition. All temporary piles would be installed using a vibratory hammer or push-in method. They would be extracted using vibratory methods or direct pull. Piles would be installed and removed continuously throughout the demolition process.

Table 6—Summary of Barges and Temporary Piles Used in Bridge Demolition

Application

Locations

Barges per

location

Piles per barge

Total piles

Duration in water

(days/location)

Span removal

4-6

160

Pier demolition

144

Total

304

Equipment required for bridge demolition includes barge-mounted cranes/hammers or hydraulic rams. Vibratory hammers would be used to install and remove sheet piles for cofferdams and pipe piles for barge moorings. New permanent piles would not be required for demolition of the Columbia River bridges.

Method of Incidental Taking

Vibratory and impact pile installation and removal, and steel casing installation, may result in behavioral disturbance, constituting Level B harassment. Project construction would require the installation and removal of approximately 1,500 temporary steel piles. In addition to pile and casing installation, behavioral disturbance could also be caused by increased activity and vessel traffic, airborne sound from the equipment and human work activity, as well as underwater sound from debris removal, vessels, and physical disturbance.

Table 7 summarizes the extent, timing, and duration of impact pile driving. Impact pile driving is expected to take place only within a 31-week in-water work window, ranging from September 15 to April 15 over the bridge construction period. There would be a total of about 138 days of impact pile driving in the Columbia River and about 134 days of impact pile driving in North Portland Harbor for the entire project from the start of bridge construction in 2013 to its anticipated completion in 2017 (approximately 4.25 years for both Columbia River and North Portland Harbor Bridges). Impact pile driving in the mainstem Columbia River would occur at more than one pier complex on about 1-2 days total during the course of the approximately 4-year construction period. Impact pile driving would be restricted to approximately 45 minutes per 12-hour work day. A sound attenuation device would generally be used for all impact pile driving, with the exception of weekly testing of the attenuation device, requiring that some impact hammering occur with the device turned off in order to compare produced sound with that produced while the device is on. This would occur for a maximum of 7.5 minutes per week. Each work day would include a period of at least 12 consecutive hours with no impact pile driving in order to minimize disturbance to aquatic animals. Impact pile driving would only occur during daylight hours. Airborne sound effects from impact pile driving would occur on the same schedule as described in Table 7.

Table 7—Summary of Impact Pile Driving

Pile size

Columbia River

Duration

Days

North Portland Harbor

Duration

Days

18-24 in (without attenuation device)

7.5 min/week

2.5-5 min/week

18-24 in (with attenuation device)

45 min/day

138

45 min/day

36-48 in (without attenuation device)

7.5 min/week

2.5-5 min/week

36-48 in (with attenuation device)

45 min/day

138

45 min/day

Table 8 summarizes the extent, timing, and duration of vibratory installation of pipe pile and sheet pile. Vibratory installation of pipe pile is likely to occur throughout the entire 5-year duration of the proposed regulations period during construction of all new in-water piers or bents and for installation of mooring piles. Vibratory installation of sheet pile would only occur in the Columbia River during construction of the new Columbia River bridges and demolition of the existing Columbia River bridges. This activity would occur intermittently throughout the construction and demolition period. Vibratory activity is not restricted to an in-water work window, and therefore may take place during any time of the year. If steel casings for drilled shafts are vibrated into place, the CRC project design team estimates that installation of the 10-ft-diameter casings would take approximately 90 days in the Columbia River and 31 days in North Portland Harbor.

Table 8—Summary of Vibratory Pile Driving

Pile type

Columbia River

Duration

Days

North Portland Harbor

Duration

Days

Pipe pile

Up to 5 hours/day

1,470-1,620

Up to 5 hours/day

334

Sheet pile

Up to 24 hours/day

N/A

Steel casings

Debris removal is not certain to occur, but is included to present the fullest disclosure of potential effects. It is possible that debris removal would occur in North Portland harbor at the location of each of the new piers where

there is anecdotal evidence that riprap occurs within the pier footprints. The exact quantity of this material is unknown, but as a worst-case scenario this activity would remove approximately 90 yd

(69 m

) of material over an area of approximately 2,433 ft

(226 m

) from all piers combined. Debris removal would produce sound through use of a bucket dredge, for up to 12 hours per day for a maximum of 7 days during the November 1-February 28 in-water work window each year.

Description of Sound Sources

Sound travels in waves, the basic components of which are frequency, wavelength, velocity, and amplitude. Frequency is the number of pressure waves that pass by a reference point per unit of time and is measured in Hz or cycles per second. Wavelength is the distance between two peaks of a sound wave; lower frequency sounds have longer wavelengths than higher frequency sounds, which is why the lower frequency sound associated with the proposed activities would attenuate more rapidly in shallower water. Amplitude is the height of the sound pressure wave or the `loudness' of a sound and is typically measured using the decibel (dB) scale. A dB is the ratio between a measured pressure (with sound) and a reference pressure (sound at a constant pressure, established by scientific standards). It is a logarithmic unit that accounts for large variations in amplitude; therefore, relatively small changes in dB ratings correspond to large changes in sound pressure. When referring to sound pressure levels (SPLs; the sound force per unit area), sound is referenced in the context of underwater sound pressure to 1 microPascal (μPa). One pascal is the pressure resulting from a force of one newton exerted over an area of one square meter. The source level represents the sound level at a distance of 1 m from the source (referenced to 1 μPa). The received level is the sound level at the listener's position.

Root mean square (rms) is the quadratic mean sound pressure over the duration of an impulse. Rms is calculated by squaring all of the sound amplitudes, averaging the squares, and then taking the square root of the average (Urick, 1975). Rms accounts for both positive and negative values; squaring the pressures makes all values positive so that they may be accounted for in the summation of pressure levels (Hastings and Popper, 2005). This measurement is often used in the context of discussing behavioral effects, in part because behavioral effects, which often result from auditory cues, may be better expressed through averaged units than by peak pressures.

When underwater objects vibrate or activity occurs, sound-pressure waves are created. These waves alternately compress and decompress the water as the sound wave travels. Underwater sound waves radiate in all directions away from the source (similar to ripples on the surface of a pond), except in cases where the source is directional. The compressions and decompressions associated with sound waves are detected as changes in pressure by aquatic life and man-made sound receptors such as hydrophones.

The underwater acoustic environment consists of ambient sound, defined as environmental background sound levels lacking a single source or point (Richardson

et al.,

1995). The ambient underwater sound level of a region is defined by the total acoustical energy being generated by known and unknown sources, including sounds from both natural and anthropogenic sources. These sources may include physical (e.g., waves, earthquakes, ice, atmospheric sound), biological (e.g., sounds produced by marine mammals, fish, and invertebrates), and anthropogenic sound (e.g., vessels, dredging, aircraft, construction). Known sound levels and frequency ranges associated with anthropogenic sources similar to those that would be used for this project are summarized in Table 9. Details of each of the sources are described in the following text.

Table 9—Representative Sound Levels of Anthropogenic Sources

Sound source

Frequency range

(Hz)

Underwater sound level

(dB re 1 μPa)

Reference

Small vessels

250-1,000

151 dB rms at 1 m

Richardson

et al.,

1995.

Tug docking gravel barge

200-1,000

149 dB rms at 100 m (328 ft)

Blackwell and Greene, 2002.

Vibratory driving of 72-in (1.8 m) steel pipe pile

10-1,500

180 dB rms at 10 m (33 ft)

Caltrans, 2007.

Impact driving of 36-in (0.9 m) steel pipe pile

10-1,500

195 dB rms at 10 m

WSDOT, 2007.

Impact driving of 66-in (1.7 m) CISS

piles

100-1,500

195 dB rms at 10 m

Reviewed in Hastings and Popper, 2005.

CISS = cast-in-steel-shell.

The CRC project would produce underwater sound through installation of piles for temporary in-water work platforms and temporary barge moorings, and vibratory installation of steel casings for drilled shafts. Piles would be installed by using impact and/or vibratory hammers, or by press-in techniques that do not produce notable underwater sound.

Several types of impact hammers are commonly used to install in-water piles: air-driven, steam-driven, diesel-driven, and hydraulic. 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). Table 10 summarizes observed underwater sound levels generated by driving various types and sizes of piles. 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.

Table 10—Summary of Observed Underwater Sound Levels Generated by Impact Pile Driving

Pile size, in (m)

Driver type

dB Peak

dB rms

12 (0.3)

Impact

208

191

14 (0.4)

Impact

195

180

16 (0.4)

Impact

200

187

24 (0.6)

Impact

212

189

30 (0.8)

Impact

212

195

36 (0.9)

Impact

214

201

60 (1.5)

Impact

210

195

66 (1.7)

Impact

210

195

96 (2.4)

Impact

220

205

126 (3.2)

Impact

213

202

150 (3.8)

Impact

200

185

Vibratory

171

155

24 (sheet), typical

Vibratory

175

160

24 (sheet), loudest

Vibratory

182

165

36 (typical)

Vibratory

180

170

36 (loudest)

Vibratory

185

175

72 (typical) (1.8)

Vibratory

183

170

72 (loudest)

Vibratory

195

180

Source: Caltrans, 2009

Note:

Sound levels measured at a distance of 10 m except where indicated by the following footnotes:

30 m;

9 m;

11 m;

100 m.

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).

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).

Table 10 outlines typical sound levels produced by installation of various types of pile using a vibratory pile driver. Note that peak sound levels range from 171 to 195 dB, whereas peak sound levels generated by impact pile driving range from 195 to 220 dB.

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). Please see Southall

et al.

(2007) for an in-depth discussion of these concepts.

Pulsed sounds (e.g., explosions, gunshots, sonic booms, seismic pile driving pulses, and impact pile driving) are brief, broadband, atonal transients (ANSI, 1986; Harris, 1998) and occur either as isolated events or repeated in some succession. Pulsed sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a decay period that may include a period of diminishing, oscillating maximal and minimal pressures. Pulsed sounds generally have an increased capacity to induce physical injury as compared with sounds that lack these features.

Non-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 Attenuation Devices

Sound levels can be greatly reduced during impact pile driving using sound attenuation devices. There are several types of sound attenuation devices including bubble curtains, cofferdams, and isolation casings. Three types of attenuation devices are described here.

Bubble curtains create a column of air bubbles rising around a pile from the substrate to the water surface. The air bubbles absorb and scatter sound waves emanating from the pile, thereby reducing the sound energy. Bubble curtains may be confined or unconfined. An unconfined bubble curtain may consist of a ring seated on the substrate and emitting air bubbles from the bottom. An unconfined bubble curtain may also consist of a stacked system, that is, a series of multiple rings placed at the bottom and at various elevations around the pile. Stacked systems may be more effective than non-stacked systems in areas with high current and deep water (Caltrans, 2009).

A confined bubble curtain contains the air bubbles within a flexible or rigid sleeve made from plastic, cloth, or pipe. Confined bubble curtains generally offer higher attenuation levels than unconfined curtains because they may physically block sound waves and they prevent air bubbles from migrating away from the pile. For this reason, the confined bubble curtain is commonly used in areas with high current velocity (Caltrans, 2009). In Oregon, confined bubble curtains are typically required where current velocity is 0.6 m/s or greater (NMFS, 2008a).

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

An isolation casing is a hollow pipe that surrounds the pile, isolating it from the in-water work area. The casing is dewatered before pile driving. This device provides levels of sound attenuation similar to that of bubble curtains; however, attenuation rates are not as great as those achieved by cofferdams because the dewatered area between the pile and the water column is generally much smaller (Caltrans, 2009).

Both environmental conditions and the characteristics of the sound attenuation device may influence the effectiveness of the device. According to Caltrans (2009):

• In general, confined bubble curtains attain better sound attenuation levels in areas of high current than unconfined bubble curtains. If an unconfined device is used, high current velocity may sweep bubbles away from the pile, resulting in reduced levels of sound attenuation.

• Softer substrates may allow for a better seal for the device, preventing leakage of air bubbles and escape of sound waves. This increases the effectiveness of the device. Softer substrates also provide additional attenuation of sound traveling through the substrate.

• Flat bottom topography provides a better seal, enhancing effectiveness of the sound attenuation device, whereas sloped or undulating terrain reduces or eliminates its effectiveness.

• Air bubbles must be close to the pile; otherwise, sound may propagate into the water, reducing the effectiveness of the device.

• Harder substrates may transmit ground-borne sound and propagate it into the water column.

The literature presents a wide array of observed attenuation results (see, e.g., WSF, 2009; WSDOT, 2008; USFWS, 2009; Caltrans, 2009). The variability in attenuation levels is due to variation in design, as well as differences in site conditions and difficulty in properly installing and operating in-water attenuation devices. WSDOT personnel have observed that, on average, unconfined bubble curtains typically achieve 9 dB of attenuation while confined bubble curtains achieve 12 dB. Caltrans (2009) offers the following generalizations:

• For steel or concrete pile 24 in (0.6 m) in diameter or less, bubble curtains would generally reduce sound levels by 5 dB.

• For steel pile measuring 24 to 48 in (0.6-1.2 m), bubble curtains may reduce sound levels by about 10 dB.

• For piles greater than 48 in diameter, bubble curtains may reduce sound levels by about 20 dB.

• As a general rule, reductions of greater than 10 dB cannot be reliably predicted.

Sound Thresholds

Since 1997, NMFS has used generic sound exposure thresholds to determine when an activity in the ocean that produces sound might result in impacts to a marine mammal such that a take by harassment 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 level sounds is that cetaceans and pinnipeds exposed to impulsive sounds of 180 and 190 dB rms or above, respectively, are considered to have been taken by Level A (i.e., injurious) harassment. Behavioral harassment (Level B) is considered to have occurred when marine mammals are exposed to sounds at or above 160 dB rms for impulse sounds (e.g., impact pile driving) and 120 dB rms for non-pulsed sound (e.g., vibratory pile driving), but below injurious thresholds. For airborne sound, pinniped disturbance from haul-outs has been documented at 100 dB (unweighted) for pinnipeds in general, and at 90 dB (unweighted) for harbor seals. NMFS uses these levels as guidelines to estimate when harassment may occur.

Distance to Sound Thresholds

The extent of project-generated sound both in and over water was calculated for the locations where pile driving would occur in the Columbia River and North Portland Harbor. The extent of underwater sound was modeled for several pile driving scenarios:

• For two sizes of pile: 18- to 24-in (0.5-0.6 m) pile and 36- to 48-in (0.9-1.2 m) pile.

• For single impact pile drivers operating both with and without an attenuation device. Use of an attenuation device was assumed to decrease initial SPLs by 10 dB (see discussion previously in this document).

• For vibratory driving of pipe pile and sheet pile.

Underwater Sound

—Models may be used to estimate the distances and areas within which sound is likely to exceed certain threshold levels. Please note that the results of such modeling are described here to provide a frame of reference for the reader. Actual distances and areas within which sound is likely to exceed certain threshold levels are known from collection of site-specific hydroacoustic monitoring data (see `Test Pile Project', later in this document).

In the absence of site-specific data, the practical spreading loss model may be 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

)

is the distance from the source for which SPLs need to be known, and D

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

× 10

(TL/15)

where TL stands for transmission loss (the difference in decibel levels between D

and D

). For example, using the distance to an injury threshold (D

), 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 CRC project were considered. WSDOT and the California Department of Transportation (Caltrans) have compiled hydroacoustic monitoring data from in-water impact pile driving. No projects with hydroacoustic monitoring data and similar site conditions were identified in the Columbia River.

A review of WSDOT and Caltrans projects containing in-water pile driving found projects in California had the most similar substrates and depths; however, only one project used 48-in pile, the largest size in the CRC project. This work occurred in the Russian River, which was only 15 m wide and 0.6 m deep at the project location. Therefore, the results are not applicable to the CRC project. Instead, data from projects that drove 36-in pile were used, using the highest sound levels

encountered as proxy values for 48-in pile.

Maximum measured sound levels from 36-in steel pile installation were 201 dB rms (WSDOT, 2008), as shown in Table 10. Site conditions for this project, in Puget Sound, are somewhat comparable to the Columbia River, as both are large, with similar depths. The maximum source level from the next largest pile size, 60-in (1.5-m) pile, was 195 dB rms at 10 m. As such, the use of data from the 36-in pile measurements provides a more conservative estimate. The CRC project would also drive 18- to 24-in diameter steel pile. Conservatively, the highest recorded value of 189 dB rms for this range of pile sizes was used (see Table 10).

No studies were available that measured site-specific initial sound levels generated by vibratory pile driving in the Region of Activity. However, Table 10 outlines a range of typical sound levels produced by vibratory pile driving as measured by Caltrans during hydroacoustic monitoring of several construction projects (Caltrans, 2009). A worst-case scenario of installing 48-in steel pipe pile (the largest pile size to be used on the CRC project) at the loudest measured SPLs was considered, however, as there were no data for 48-in pile, it was assumed that sound levels for 48-in pile would be intermediate between those levels generated by 36-in pile and 72-in (1.8-m) pile. Typical values for both 36- and 72-in pile were 170 dB, while the loudest values were 175 dB for 36-in pile and 180 dB for 72-in pile. Thus, 175 dB was considered an appropriate value for initial SPLs for vibratory driving of pipe pile. The project may also install sheet pile, in the Columbia River only. In general, installation of sheet pile produces lower SPLs than pipe pile. Using data presented in Table 10, an initial SPL of approximately 160 dB rms at a distance of 15 m was assumed. Table 11 shows the calculated distances required for underwater sound to attenuate to relevant thresholds, as per the practical spreading model (please see Figures B-1 to B-6 of CRC's application for graphical depictions of threshold distances discussed here).

Table 11—Calculated Distances to Sound Thresholds

Threshold

Pile size

Distance to threshold (without

attenuation

device)

(m)

Distance to threshold

(with attenuation

device)*

(m)

Injury: 190 dB rms

18-24 in

Harassment: 160 dB rms

18-24 in

858

185

Injury: 190 dB rms

36-48 in

Harassment: 160 dB rms

36-48 in

5,412

1,166

Harassment: 120 dB rms

36-72 in

23,208

n/a

Harassment: 120 dB rms

24-in sheet pile

6,962

n/a

* 10 dB reduction in SPLs assumed from use of attenuation device.

Landforms in the Columbia River and North Portland Harbor would block underwater sound well before it reaches certain calculated distances. Table 12 shows actual site-specific values for the maximum distance within which sound is likely to exceed a given threshold level until contact with landforms. Categories not listed in Table 12 would remain the same as shown in Table 11.

Table 12—Actual Distances to Sound Thresholds

Threshold

Pile size

Location*

Upstream

(m)

Downstream

(m)

Harassment: 160 dB rms

36-48 in (without attenuation)

NPH

3,058

5,412

Harassment: 120 dB rms

36-72 in

20,166

8,851

Harassment: 120 dB rms

36-72 in

NPH

3,058

5,632

* NPH = North Portland Harbor; CR = Columbia River.

Airborne Sound

—For calculating the levels and extent of project-generated airborne sound, a point sound source and hard-site conditions were assumed because pile drivers would be stationary, and work would largely occur over open water and adjacent to an urbanized landscape. Thus, calculations assumed that pile driving sound would attenuate at a rate of 6 dB per doubling distance, based on a spherical spreading model. The following formula was used to determine the distances at which pile-driving sound attenuates to the 90 dB rms and 100 dB rms (re: 20 µPa; all airborne SPLs discussed here are referenced to 20 µPa) airborne disturbance thresholds:

= D

* 10

((initial SPL−airborne disturbance threshold)/α)

where D

is the distance from the pile at which sound attenuates to the threshold value, D

is the distance from the pile at which the initial SPLs were measured, and α is the variable for soft-site or hard-site conditions. These calculations used α = 20 for hard-site conditions.

The estimate of initial sound level is based on the results of monitoring performed by WSDOT during pile driving at Friday Harbor Ferry Terminal (Laughlin, 2005b). The results showed airborne rms sound levels of 112 dB taken at 160 ft (49 m) from the source during impact pile driving. This project drove 24-in steel pipe pile, which is only half the size of the largest pile proposed for use in the CRC project. However, airborne sound levels are independent of the size of the pile (CRC, 2010), and therefore the sound levels encountered at Friday Harbor are applicable to the CRC project.

The model used 112 dB rms at 160 ft from the source as the initial sound level for a single pile driver. Because multiple pile drivers would not strike

piles synchronously, operation of multiple pile drivers would not generate sound louder than that of a single pile driver. Therefore, initial sound levels for multiple pile drivers were assumed to be the same as for a single pile driver. The CRC project is not likely to use an airborne sound-attenuation device. Sound generated by impact pile driving in the Columbia River and North Portland Harbor is likely to exceed the 100 dB rms airborne disturbance threshold within 195 m of the source and is likely to exceed the 90 dB rms airborne disturbance threshold within 650 m of the source.

Debris Removal

—Debris removal may occur in North Portland Harbor at the location of each of the new piers where there is anecdotal evidence that riprap occurs within the pier footprints. Debris removal in the North Portland Harbor, if it occurs, is likely to create sound at or above the 120-dB disturbance threshold for continuous sound in underwater portions of the Region of Activity.

Few studies have been conducted on sound emissions produced by underwater debris removal. A review of the literature indicates that underwater debris removal would produce sound in the range of 135 dB to 147 dB at 10 m (Dickerson

et al.,

2001; OSPAR, 2009; Thomsen

et al.,

2009).

Underwater debris removal is not expected to generate significant airborne sound. The air-water interface creates a substantial sound barrier and reduces the intensity of underwater sound waves by a factor of more than 1,000 when they cross the water surface. The above-water environment is, thus, virtually insulated from the effects of underwater sound (Hildebrand, 2005). Therefore, underwater debris removal is not expected to measurably increase ambient airborne sound. Underwater sound from debris removal would likely attenuate to the 120-dB underwater disturbance threshold for continuous sound within 631 m of the source. This activity would occur for only 7 days, during the in-water work window.

Test Pile Project

In February 2011, CRC conducted a test pile project in order to acquire geotechnical and sound propagation data to assess site-specific characteristics and verify the modeling results discussed in the preceding section, and to assess mitigation measures related to pile installation activities planned for the CRC project. Please see CRC's Test Pile Hydroacoustic Monitoring Report for detailed analysis (

SUPPLEMENTARY INFORMATION

Engineering objectives included the following:

• Determine strike numbers necessary to install piles to reach load-bearing capacity with an impact hammer;

• Identify suitable equipment and materials and verify production rates for pile installation;

• Determine the feasibility of vibratory installation methods; and

• Validate geotechnical and engineering calculations.

Environmental objectives included the following:

• Determine the underwater sound levels resulting from vibratory installation of temporary piles in the predominant substrate types found at typical mid-channel depths at the project site;

• Determine the underwater sound levels resulting from impact installation of temporary piles in the predominant substrate types found at typical mid-channel depths at the project site;

• Determine the effectiveness of two sound attenuation strategies (unconfined and confined bubble curtains) during impact pile driving;

• Determine the transmission loss of pile installation sound for both impact and vibratory installation;

• Determine the extent of construction sound impacts in-air for impact pile driving; and

• Determine the extent of turbidity plumes resulting from vibratory and impact pile installation and extraction, and from unconfined and confined bubble curtain operation.

Test pile operations consisted of impact driving or vibratory driving at six pile locations using 24- and 48-in piles. A confined or unconfined bubble curtain was tested during each pile installation. Background sound level monitoring was successfully conducted between January 27 and February 3, 2011. The background sound level at fifty percent cumulative distribution function (CDF) on the Washington (north) side of the river was found to be 110 dB, while the background level at fifty percent CDF on the Oregon (south) side of the river was slightly higher at 117 dB.

Hydroacoustic monitoring was successfully conducted during test pile construction activities February 11-21, 2011. Rms pressure levels associated with vibratory driving varied widely pile to pile; subsurface driving conditions are the likely cause of this variability. For impact driving, average sound levels were derived for both 24-in and 48-in piles. Impact driving on 48-in piles was, on average, 10 dB louder than driving on 24-in piles.

Measured sound levels for both vibratory driving and impact driving were similar to those expected as outlined previously in this document. For vibratory driving, the maximum observed sound level was 181 dB, only slightly louder than the anticipated maximum sound level (180 dB). For impact driving, observed unattenuated rms sound levels for 24-in piles were 191 dB, slightly louder than anticipated (189 dB). Unattenuated rms sound levels for 48-in piles (201 dB) were as anticipated. The average rms pressure level for vibratory pile extraction was 173 dB, and did not appear to vary with pile size. The 173 dB observed for extraction was slightly less than the 176 dB average observed during pile installation. The variance of the pressure levels was also less, with extraction values ranging from 167-176 dB while installation values ranged from 157-181 dB.

Open curtain attenuation methods reduced the sound levels for 48-in piles 11 dB on average, and 9 dB on average for 24-in piles. Confined curtain attenuation methods reduced the sound levels for 48-in piles 13 dB on average, and 8.5 dB on average for 24-in piles. Open bubble curtain attenuation was similar to confined curtain attenuation at 10 m downstream; however, the effectiveness of the open bubble curtain appeared to be significantly less upstream when compared to downstream, likely due to the effect of current on the open bubble curtain. The observed effectiveness of both open and confined bubble curtains at attenuating peak amplitudes (8-13 dB) was approximately as anticipated (10 dB).

Transmission loss was analyzed for both vibratory driving and impact driving. Transmission loss for vibratory driving was in line with the practical spreading model, as anticipated. However, this analysis is based on results from only one pile; for two of the piles, the signal could not be distinguished from background noise at 200 m, while for a third pile, the signal could not be distinguished from background noise at 800 m. Thus, transmission loss could not be calculated for those piles, although energy from those piles clearly showed rapid attenuation. Transmission loss for impact driving was in line with the practical spreading model at the 200-m range, but steadily increased toward spherical spreading with increasing range, resulting in greater than anticipated transmission loss.

The data for transmission loss associated with vibratory driving suggest that the majority of the energy occurs in frequencies below 1,000 Hz,

with energy levels gradually falling off at higher frequencies (CRC, 2011). For vibratory installation in this study, driving of two piles produced energy that could not be distinguished from background by 200 m, while the signal from a third could not be detected at the 800 m station. The signal was distinguishable from background sound levels at approximately 800 m for only one of the piles, indicating that distance to the threshold would likely be less than the modeling results predicted. However, background sound levels during pile driving were higher than those measured previously. It is possible that increased background levels resulted from sound associated with the project, instrumentation, or some other source. Nevertheless, data indicate that transmission loss for vibratory driving is approximately in conformance with practical spreading loss. Piles were generally installed or extracted during the test pile study in less than 5 minutes (ranging from less than 1 minute to less than 10 minutes, for all but one outlier).

Measured, site-specific values were either substantially similar to assumed values or, in the case of transmission loss or realized attenuation from use of bubble curtains in certain circumstances, the assumed values described previously in this document were more conservative than the actual values. As such, those values remain valid but likely represent a significantly more conservative scenario than would realistically occur. Actual distances to be monitored for potential injury or harassment of pinnipeds would be based on the results of in-situ hydroacoustic monitoring, where relevant, and are discussed in greater detail in `Proposed Mitigation', later in this document.

Comments and Responses

On December 15, 2010, NMFS published a notice of receipt of an application for a Letter of Authorization (LOA) in the

Federal Register

(75 FR 78228) and requested comments and information from the public for 30 days. NMFS did not receive any substantive comments.

Description of Marine Mammals in the Area of the Specified Activity

Marine mammal species that have been observed within the Region of Activity consist of the harbor seal, California sea lion, and Steller sea lion. Pinnipeds follow prey species into freshwater up to, primarily, the Bonneville Dam (RM 145, RKm 233) in the Columbia River, but also to Willamette Falls in the Willamette River (RM 26, RKm 42). The Willamette River enters the Columbia River approximately 5 mi (8 km) downstream of the CRC project area and is within the Region of Activity. Harbor seals rarely, but occasionally, transit the Region of Activity. The eastern population of the Steller sea lion is listed as threatened under the ESA and as depleted and strategic under the MMPA. Neither the California sea lion nor the harbor seal is listed under the ESA, nor are they considered depleted or strategic under the MMPA.

The sea lions use this portion of the river primarily for transiting to and from Bonneville Dam, which concentrates adult salmonids and sturgeon returning to natal streams, providing for increased foraging efficiency. The U.S. Army Corps of Engineers (USACE) has conducted surface observations to evaluate the seasonal presence, abundance, and predation activities of pinnipeds in the Bonneville Dam tailrace each year since 2002. This monitoring program was initiated in response to concerns over the potential impact of pinniped predation on adult salmonids passing Bonneville Dam in the spring. An active sea lion hazing, trapping, and permanent removal program was in place below the dam from 2008 through 2010. Much of the information presented in this application is based on research conducted as part of the Bonneville Dam sea lion program.

Pinnipeds remain in upstream locations for a couple of days or longer, feeding heavily on salmon, steelhead, and sturgeon (NOAA 2008), although the occurrence of harbor seals near Bonneville Dam is much lower than sea lions (Stansell

et al.,

2009). Sea lions congregate at Bonneville Dam during the peaks of salmon return, from March through May each year, and a few California sea lions have been observed feeding on salmonids in the area below Willamette Falls during the spring adult fish migration (NOAA, 2008).

There are no pinniped haul-out sites in the Region of Activity. The nearest haul-out sites, shared by harbor seals and California sea lions, are near the Cowlitz River/Carroll Slough confluence with the Columbia River, approximately 45 mi (72 km) downriver from the Region of Activity (Jeffries

et al.,

2000). The nearest known haul-out for Steller sea lions is a rock formation (Phoca Rock) near RM 132 (RKm 212) approximately 8 mi (13 km) downstream of Bonneville Dam and 26 mi (42 km) upstream from the Region of Activity. Steller sea lions are also known to haul out on the south jetty at the mouth of the Columbia River, near Astoria, Oregon. There are no pinniped rookeries located in or near the Region of Activity.

Harbor Seal

Species Description

—Harbor seals, which are members of the Phocid family (true seals), inhabit coastal and estuarine waters and shoreline areas from Baja California, Mexico to western Alaska. For management purposes, differences in mean pupping date (i.e., birthing) (Temte, 1986), movement patterns (Jeffries, 1985; Brown, 1988), pollutant loads (Calambokidis

et al.,

1985) and fishery interactions have led to the recognition of three separate harbor seal stocks along the west coast of the continental U.S. (Boveng, 1988). The three distinct stocks are: (1) Inland waters of Washington (including Hood Canal, Puget Sound, and the Strait of Juan de Fuca out to Cape Flattery), (2) outer coast of Oregon and Washington, and (3) California (Carretta

et al.

2007b). The seals in the Region of Activity are from the outer coast of Oregon and 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 population of the Oregon/Washington coastal stock of harbor seals was estimated at 24,732 animals (Carretta

et al.,

2007a). 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. This harbor seal stock includes coastal estuaries (Columbia River) and bays (Willapa Bay and Grays Harbor). Both the Washington and Oregon portions of this stock are believed to have reached carrying capacity and the stock is within its optimum sustainable population level (Jeffries

et al.,

2003; Brown

et al.,

2005). Because there is no current estimate of minimum abundance, potential biological removal (PBR) cannot be calculated for this stock. However, the level of human-caused mortality and serious injury is less than ten percent of the previous PBR of 1,343 harbor seals per year (Carretta

et al.,

2007), and human-caused mortality is considered to be small relative to the stock size. Therefore, the Oregon and Washington outer coast stock of harbor seals are not classified as a strategic stock under the MMPA.

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 Oregon and 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 Oregon and 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 two states. Numerous harbor seal haul-out sites are found on intertidal mudflats and sand bars from the mouth of the lower Columbia River to Carroll Slough at the confluence of the Cowlitz and Columbia Rivers.

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 coastal estuaries (Columbia River, Willapa Bay, and Grays Harbor) from mid-April through June and in other areas along the Olympic Peninsula and Puget Sound from May through September (WDFW, 2000). Suckling harbor seal pups spend as much as forty percent of their time in the water (Bowen

et al.,

1999).

They can be found throughout the year at the mouth of the Columbia River. Peak harbor seal abundances in the Columbia River occur during the winter and spring when a number of upriver haul-out sites are used. Peak abundances and upriver movements in the winter and spring months are correlated with spawning runs of eulachon (

Thaleichthys pacificus

) smelt and out-migration of salmonid smolts. Harbor seals are infrequently observed at Bonneville Dam or in the Region of Activity. In 2009 and again in 2010, two harbor seals were observed at the dam (Stansell

et al.,

2009; Stansell and Gibbons, 2010), and observations of harbor seals at Bonneville Dam have ranged from one to three per year from 2002 to 2010.

Within the Region of Activity, there are no known harbor seal haul-out sites. The nearest known haul-out sites to the Region of Activity are located at Carroll Slough at the confluence of the Cowlitz and Columbia Rivers approximately 45 mi (72 km) downriver of the Region of Activity. The low number of observations of harbor seals at Bonneville Dam over the years, combined with the fact that no pupping or haul-out locations are within or upstream from the Region of Activity, suggest that very few harbor seals transit through the Region of Activity (Stansell

et al.,

2010).

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 Lions

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 U.S. stock of California sea lions is estimated at 238,000 and the minimum population size of this stock is 141,842 individuals (Carretta

et al.,

2007). These numbers are from counts during the 2001 breeding season of animals that were ashore at the four major rookeries in southern California and at haul-out sites north to the Oregon/California border. Sea lions that were at-sea or hauled-out at other locations were not counted (Carretta

et al.,

2007). The stock has likely reached its carrying capacity and, even though current total human-caused mortality is unknown (due a lack of observer coverage in the California set gillnet fishery that historically has been the largest source of human-caused mortalities), California sea lions are not considered a strategic stock under the

MMPA because total human-caused mortality is still likely to be less than the PBR.

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

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 Oregon. Though a few young animals may remain in Oregon during summer months, most return south for the breeding season (ODFW, 2010). Male California sea lions are commonly seen in Oregon from September through May. During this time period California sea lions can be found in many bays, estuaries and on offshore sites along the coast, often hauled-out in the same locations as Steller sea lions. Some pass through Oregon to feed along coastal waters to the north during fall and winter months (ODFW, 2010).

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.

California sea lions are known to occur in several areas of the Columbia River during much of the year, except the summer breeding months of June through August. Approximately 1,000 California sea lions have been observed at haul-out sites at the mouth of the Columbia River, while approximately 100 individuals have been observed in past years at the Bonneville Dam between January and May prior to returning to their breeding rookeries in California at the end of May (Stansell, 2010). The nearest known haul-out sites to the Region of Activity are near the Cowlitz River/Carroll Slough confluence with the Columbia River, approximately 45 mi (72 km) downriver of the Region of Activity (Jeffries

et al.,

2000).

The USACE's intensive sea lion monitoring program began as a result of the 2000 Federal Columbia River Power System (FCRPS) biological opinion, which required an evaluation of pinniped predation in the tailrace of Bonneville Dam. The objective of the study was to determine the timing and duration of pinniped predation activity, estimate the number of fish caught, record the number of pinnipeds present, identify and track individual California sea lions, and evaluate various pinniped deterrents used at the dam (Tackley

et al.,

2008a). The study period for monitoring was January 1 through May 31, beginning in 2002. During the study period, pinniped observations began after consistent sightings of at least one animal occurred. Tackley

et al.

(2008a) note that sightings began earlier each year from 2002 to 2004. Although some sightings were reported earlier in the season, full-time observations began March 21 in 2002, March 3 in 2003, and February 24 in 2004 (Tackley

et al.,

2008a). In 2005 observations began in April, but in 2006 through 2010 observations began in January or early February (Tackley

et al.,

2008a, 2008b; Stansell

et al.,

2009; Stansell and Gibbons, 2010). In 2009, 54 California sea lions were observed at Bonneville Dam, the fewest since 2002 (Stansell

et al.,

2009). However, in 2010, 89 California sea lion individuals were observed at Bonneville Dam (Stansell

et al.,

2010). In addition, up to four California sea lions have been observed at Bonneville Dam during the September-January period in recent years (CRC, 2010).

Up to eight California sea lions have been observed in recent years feeding on salmonids in the Willamette River below Willamette Falls (NOAA, 2008). The earliest known report of California sea lions at Willamette Falls was in 1975, when two sea lions were reported taking salmon and hindering fish passage at the fish ladder. Other than the 1975 sighting, there were no reports of sea lions at Willamette Falls until the late 1980s when personnel at the fish ladder reported California sea lion sightings below the falls. California sea lions were sighted sporadically near the falls until 1995 when they began occurring almost daily from February through late May (Scordino, 2010).

California sea lion arrival and departure dates at Bonneville Dam are compiled in Table 13 from the reports listed in the preceding paragraph. If arrival and departure dates were not available, the timing of surface observations within the January through May study period were recorded. Because regular observations in the study period generally began as California sea lions were observed below Bonneville Dam, and sometimes reports stated that observations stopped as sea lion numbers dropped, the observation dates only give a general idea of first arrival and departure. Because tracking data indicate that sea lions travel at fast rates between hydrophone locations above and below the CRC project area, dates of first arrival at Bonneville Dam and departure from the dam are assumed to coincide closely with potential passage timing through the CRC project area.

Table 13—Arrival and Departure Dates for California Sea Lions Below Bonneville Dam

2002

2003

2004

2005

2006

2007

2008

2009

2010

Arrival

3-21

3-03

2-24

4-11/1-21

2-09

1-08

1-11

1-14

1-08

Departure

5-24

6-02

5-30

5-31/6-10

6-02

5-26

5-31

5-19

6-04

Dates are dates observations were taken and not when sea lions were first seen. In 2005 through 2007, observations were made intermittently until sea lions were seen consistently (Tackley

et al.,

2008a). In 2005, surface observations were made from April 11 through May 31. However, the first California sea lion arrived January 21 and departed on June 10 (Tackley

et al.,

2008a).

A single sighting was made on November 7 (Tackley

et al.,

2008a).

Three California sea lions were observed between September and December 2008. These observations were opportunistic and outside the regular observation period of January through May (Stansell

et al.,

2009).

Observations ended because few sea lions were present. One California sea lion was in the Bonneville Dam forebay through at least August 11 (Stansell

et al.,

2009).

Based on the information presented in Table 13, California sea lions have generally been observed at Bonneville Dam between early January and early June, although beginning in 2008, a few individuals have been noted at the dam as early as September and as late as August. Therefore, the majority of California sea lions are expected to pass the project site beginning in early January through early June. Stansell and Gibbons (2010) and Stansell

et al.

(2009) show that California sea lion abundance below Bonneville Dam peaks in April, when it drops through about the end of May. In 2010, California sea lions stayed below the dam until almost mid-June, which was late historically and enters into the time they normally depart for southern breeding grounds. Wright

et al.

(2010) reported a median start date for the southbound migration from the Columbia River to the breeding grounds of May 20 (range: May 7 to May 27; n = 8 sea lions).

The highest number of California sea lions observed in the Bonneville Dam tailrace over the last 9 years was 104 in 2003 (Stansell

et al.,

2010). However, Tackley

et al.

(2008a) noted that numbers of sea lions estimated from early study years were likely underestimated, because the observers' ability to uniquely identify individuals increased over the years. In addition, the high number of 104 individuals present below the dam in 2003 occurred prior to hazing (2005) or permanent removal (2008) activities began. The high for the 2008 through 2010 time period is a minimum of 89 individuals in a year (Stansell

et al.,

2010).

The Pacific States Marine Fisheries Commission (PSMFC) leads a tagging and tracking program for California sea lions, observing that the transit time for California sea lions between Astoria and Bonneville Dam is 30-36 hours upstream, and 15 hours downstream (CRC, 2010). ODFW studied the migration of male California sea lions during the nonbreeding season by satellite tracking 26 sea lions captured in the lower Columbia River over the course of three non-breeding seasons between November and May in 2003-04, 2004-05, and 2006-07.

Fourteen of the sea lions had previously been observed in the Columbia River (`river type') and twelve animals were `unknown' types. Wright

et al.

(2010) found there was considerable within and between individual variation in spatial and temporal movements, which presumably reflected variation in foraging behavior. Many sea lions repeatedly alternated between several haul-out sites throughout the non-breeding season.

Twenty of the 26 satellite-tagged sea lions remained within the waters of Oregon and Washington during the time they were monitored; the remainder made forays north to British Columbia or south to California. All fourteen of the previously known `river' sea lions were later documented upriver (either by tracking or direct observation); none of the twelve `unknown' animals were detected upriver. Southward departure dates from the Columbia River ranged from May 7 to June 17. Travel time to the breeding grounds ranged from 12 to 21 days. Only one animal was tracked back to the Columbia River; it returned on August 18 after a 21-day trip from San Miguel Island (Wright

et al.,

2010). Movement of sea lions to the base of Bonneville Dam to forage on salmonids was documented in only a fraction of the sea lions tracked, which suggested that the problem of pinniped predation on Columbia River salmonid stocks should be addressed primarily at upriver sites such as Bonneville Dam rather than in the estuary where sea lions of many behavioral types co-occur (Wright

et al.,

2010).

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

Status

—Steller sea lions were listed as threatened range-wide under the ESA in 1990. After division into two DPSs, the western DPS was listed as endangered under the ESA in 1997, while the eastern DPS remained classified as threatened. Animals found

in the Region of Activity are from the eastern DPS (NMFS, 1997a; Loughlin, 2002; Angliss and Outlaw, 2005). 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 I, Southeast Farallon I, and Sugarloaf Island and Cape Mendocino) are designated critical habitat (NMFS, 1993). There is no designated critical habitat within the Region of Activity.

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 Oregon and Washington was 5,813 in 2002 (Pitcher

et al.,

2007; Allen and Angliss, 2010). Counts in Oregon have shown a gradual increase from 1,486 animals in 1976 to 4,169 animals in 2002 (NMFS, 2008b).

The abundance of the eastern DPS of Steller sea lions is increasing throughout the northern portion of its range (southeast Alaska and British Columbia), and stable or increasing in the central portion (Oregon through central California). Surveys indicate that pup production in Oregon increased at 3 percent per year from 1990-2009, while pup production in California increased at 5 percent per year between 1996 and 2009, with the number of non-pups reported as stable. The best available information indicates that, overall, the eastern DPS has increased from an estimated 18,040 animals in 1979 to an estimated 63,488 animals in 2009; therefore the overall estimated rate of increase for this period is 4.3 percent per year (NMML, 2012).

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 (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 (1927-47), 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 gregarious animals that often travel or haul out in large groups of up to 45 individuals (Keple, 2002). At sea, groups usually consist of female and subadult males; adult males are usually solitary while at sea (Loughlin, 2002). In the Pacific Northwest, breeding rookeries are located in British Columbia, Oregon, and northern California. Steller sea lions form large rookeries during late spring when adult males arrive and establish territories (Pitcher and Calkins, 1981). Large males aggressively defend territories while non-breeding males remain at peripheral sites or haul-outs. Females arrive soon after and give birth. Most births occur from mid-May through mid-July, and breeding takes place shortly thereafter. Most pups are weaned within a year. Non-breeding individuals may not return to rookeries during the breeding season but remain at other coastal haul-outs (Scordino, 2006).

Steller sea lions are opportunistic predators, feeding primarily on fish and cephalopods, and their diet varies geographically and seasonally (Bigg, 1985; Merrick

et al.,

1997; Bredesen

et al.,

2006; Guenette

et al.,

2006). Foraging habitat is primarily shallow,

nearshore and continental shelf waters; freshwater rivers; and also deep waters (Reeves

et al.,

2008; Scordino, 2010).

In Oregon, Steller sea lions are found on offshore rocks and islands. Most of these haul-out sites are part of the Oregon Islands National Wildlife Refuge and are closed to the public (ODFW, 2010). Oregon is home to the largest breeding site in U.S. waters south of Alaska, with breeding areas at Three Arch Rocks (Oceanside), Orford Reef (Port Orford), and Rogue Reef (Gold Beach). Steller sea lions are also found year-round in smaller numbers at Sea Lion Caves and at Cape Arago State Park.

Although Steller sea lions occur primarily in coastal habitat in Oregon and Washington, they are present year-round in the lower Columbia River, usually downstream of the confluence of the Cowlitz River (ODFW, 2008). However, adult and subadult male Steller sea lions have been observed at Bonneville Dam, where they prey primarily on sturgeon and salmon that congregate below the dam. In 2002, the USACE began monitoring seasonal presence, abundance, and predation activities of marine mammals in the Bonneville Dam tailrace (Tackley

et al.,

2008b). Steller sea lions have been documented every year since 2003; observations have steadily increased to 75 Steller sea lions in 2010, the most on record and almost triple the number of the previous year (26 individuals) (Stansell

et al.,

2009, 2010).

Steller sea lions use the Columbia River for travel, foraging, and resting as they move between haul-out sites and the dam. There are no known haul-out sites within the portions of the Region of Activity occurring in the Columbia River, Willamette River, or North Portland Harbor. The nearest known haul-out in the Columbia River is a rock formation (Phoca Rock) approximately 8 mi (13 km) downstream of Bonneville Dam (approximately 26 mi (42 km) upstream from the project site). Steller sea lions are also known to haul out on the south jetty at the mouth of the Columbia River, near Astoria, Oregon. There are no rookeries located in or near the Region of Activity. The nearest Steller sea lion rookery is on the northern Oregon coast at Oceanside (ODFW, 2010), approximately 70 mi (113 km) south of Astoria, i.e., more than 150 mi (240 km) from the Region of Activity.

Steller sea lions arrive at the dam in late fall (Tackley

et al.,

2008b), although occasionally individuals are sighted near Bonneville Dam in the months of September, October, and November (Stansell

et al.,

2009, 2010). Steller sea lions are present at the dam through May, and can travel between the dam and the mouth of the Columbia River several times during these months (Tackley

et al.,

2008b). Table 14 compiles data from surface observations by the USACE for the Bonneville Dam tailrace. If arrival and departure dates were not available, the timing of surface observations within the January through May study period were recorded. Because regular observations in the study period generally began when California sea lions are observed below Bonneville Dam, and sometimes reports stated that observations stopped as sea lion numbers dropped, the observation dates only give a general idea of first arrival and departure for Steller sea lions. Because tracking data indicate that sea lions travel at fast rates between hydrophone locations above and below the CRC project area (Brown

et al.,

2010), dates of first arrival at Bonneville Dam and departure from the dam are assumed to coincide closely with potential passage timing through the CRC project area.

Table 14—Arrival and Departure Dates for Steller Sea Lions Below Bonneville Dam

2002

2003

2004

2005

2006

2007

2008

2009

2010

Arrival

n/a

3-03

2-24

4-11

1,2

2-10

1,2

1-08

1,3

1-11

1,4

1-14

1,6

1-08

Departure

n/a

6-02

5-30

5-31

1,2

5-31

1,2

5-26

5-31

5-19

6-04

Dates are dates observations were taken and not when sea lions were first seen. Observations were made in 2002, but no Steller sea lions were observed. In 2005 through 2007, observations were made intermittently until sea lions were seen consistently (Tackley

et al.,

2008a). Observation dates for 2006-07 from Scordino 2010.

In 2006 and 2007 Steller sea lions were seen regularly in the tailrace area from January to early March. Report notes anecdotal information on sightings of Steller sea lions in November and December. Report states that after March when hazing activities began, fewer Steller sea lions were observed through May (Tackley

et al.,

2008a).

Steller sea lions were known to be catching and consuming sturgeon in the Bonneville Dam tailrace and farther downstream as early as November 2007 (Tackley

et al.,

2008b).

Steller sea lions were known to be catching and consuming sturgeon in the Bonneville Dam tailrace and farther downstream as early as October 2008 (Stansell

et al.,

2009).

Observations ended because few sea lions were present.

Steller sea lions were observed downriver of the Bonneville Dam tailrace as early as September 2009 (Stansell

et al.,

2010).

Based on the information presented in Table 14, Steller sea lions are expected to pass the project site beginning with a few individuals as early as September and most individuals in January through early June. Stansell

et al.

(2009, 2010) show that Steller sea lion abundance below Bonneville Dam increases through approximately mid-April, and then drops through about the end of May.

ODFW tagged eight Steller sea lions with acoustic and/or satellite-linked transmitters from March 30 through May 4, 2010 (Wright, 2010a). Data show that the eight individuals only made one or two roundtrips from Bonneville during the months they were tracked. This study is ongoing and more information will be available in the future to determine both the number of roundtrips from Bonneville and the time to transit between Bonneville and the mouth of the Columbia River. Although transit times between the mouth of the Columbia River and Bonneville Dam are not available for Steller sea lions, they are available for California sea lions. The PSMFC leads a tagging and tracking program for California sea lions, which has observed that the transit time for California sea lions between Astoria and Bonneville Dam is 30-36 hours upstream and 15 hours downstream (CRC, 2010). Similar transit times are assumed here for Steller sea lions. Steller sea lions have generally been observed at Bonneville Dam between early January and late May, although individuals have been noted at the dam as early as September (Stansell

et al.,

2010). Thus, Steller sea lions are likely to be transiting in the Columbia River and North Portland Harbor during the time that in-water work would take place.

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).

Background on Marine Mammal Hearing

When considering the influence of various kinds of sound on the marine environment, it is necessary to understand that different kinds of marine life are sensitive to different frequencies of sound. Based on available behavioral data, audiograms derived using auditory evoked potential techniques, anatomical modeling, and other data, Southall

et al.

(2007) designate functional hearing groups for marine mammals and estimate the lower and upper frequencies of functional hearing of the groups. The functional groups and the associated frequencies are indicated below (though animals are less sensitive to sounds at the outer edge of their functional range and most sensitive to sounds of frequencies within a smaller range somewhere in the middle of their functional hearing range):

• Low frequency cetaceans (mysticetes): Functional hearing is estimated to occur between approximately 7 Hz and 22 kHz;

• Mid-frequency cetaceans (dolphins, larger toothed whales, beaked and bottlenose whales): Functional hearing is estimated to occur between approximately 150 Hz and 160 kHz;

• High frequency cetaceans (true porpoises, river dolphins,

Kogia

sp.): Functional hearing is estimated to occur between approximately 200 Hz and 180 kHz; and

• Pinnipeds in water: functional hearing is estimated to occur between approximately 75 Hz and 75 kHz, with the greatest sensitivity between approximately 700 Hz and 20 kHz.

As mentioned previously in this document, three species of pinnipeds are likely to occur in the Region of Activity.

Potential Effects of the Specified Activity on Marine Mammals

CRC's in-water construction and demolition activities (e.g., pile driving and removal) introduce sound into the marine environment, and have the potential to have adverse impacts on marine mammals. The potential effects of sound from the proposed activities associated with the CRC 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.

Tolerance

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

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 in the Region of Activity.

Disturbance

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 pinnipeds. 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 x 98 ft (25 x 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).

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.”

Efforts to deter pinniped predation on salmonids below Bonneville Dam began in 2005, and have used Acoustic Deterrent Devices (ADDs), boat chasing, above-water pyrotechnics (cracker shells, screamer shells or rockets), rubber bullets, rubber buckshot, and beanbags (Stansell

et al.,

2009). Review of deterrence activities by the West Coast Pinniped Program noted “USACE observations from 2002 to 2008 indicated that increasing numbers of California sea lions were foraging on salmon at Bonneville Dam each year, salmon predation rates increased, and the deterrence efforts were having little

effect on preventing predation” (Scordino, 2010). In the USACE status report through May 28, 2010, boat hazing was reported to have limited, local, short term impact in reducing predation in the tailrace, primarily from Steller sea lions. ODFW and the WDFW reported that sea lion presence did not appear to be significantly influenced by

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