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Taking of Marine Mammals Incidental to Specified Activities; Construction of the East Span of the San Francisco-Oakland Bay Bridge

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


Notice of proposed authorization for a small take authorization; request for comments.


NMFS has received a request from the California Department of Transportation (CALTRANS) for renewal of an authorization to take small numbers of California sea lions, Pacific harbor seals, harbor porpoises, and gray whales, by harassment, incidental to construction of a replacement bridge for the East Span of the San Francisco-Oakland Bay Bridge (SF-OBB) in California. Under the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an authorization to CALTRANS to incidentally take, by harassment, small numbers of these species of pinnipeds and cetaceans during the next 12 months.


Comments and information must be received no later than February 27, 2006.


Comments on the application should be addressed to Steve Leathery, Chief, Permits, Conservation and Education Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910-3225, or by telephoning the contact listed here. The mailbox address for providing email comments is Include in the subject line of the e-mail comment the following document identifier: 112205E. Comments sent via e-mail, including all attachments, must not exceed a 10-megabyte file size. A copy of the 2001 application, the 2005 renewal request, the June 2004 Annual Report and/or the January 2005 Annual Report may be obtained by writing to this address or by telephoning one of the contacts listed here.

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Shane Guan, NMFS, (301) 713-2289, ext 137, or Monica DeAngelis, NMFS, (562) 980-3232.

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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, notice of a proposed authorization is provided to the public for review.

Permission may be granted if NMFS finds that the taking will have no more than a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses and that the permissible methods of taking and requirements pertaining to the monitoring and reporting of such taking are set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 as “* * * an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.”

Section 101(a)(5)(D) of the MMPA established an expedited process by which citizens of the United States can apply for an authorization to incidentally take small numbers of marine mammals by harassment. 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].

Section 101(a)(5)(D) establishes a 45-day time limit for NMFS review of an application followed by a 30-day public notice and comment period on any proposed authorizations for the incidental harassment of small numbers of marine mammals. Within 45 days of the close of the comment period, NMFS must either issue or deny issuance of the authorization.

Summary of Request

On October 17, 2005, CALTRANS sumbitted a request to NOAA requesting renewal of an IHA for the possible harassment of small numbers of California sea lions (Zalophus californianus), Pacific harbor seals (Phoca vitulina richardsii), harbor porpoises (Phocoena phocoena), and gray whales (Eschrichtius robustus) incidental to construction of a replacement bridge for the East Span of the SF-OBB, in San Francisco Bay (SFB or the Bay), California. An IHA was issued to CALTRANS for this activity on January 3, 2005 and it expired on January 3, 2006 (70 FR 2123). A detailed description of the SF-OBB project and background information on the issuance of this IHA were provided in the November 14, 2003 (68 FR 64595) Federal Register notice and are not repeated here. Please refer to that Federal Register notice.

Description of the Marine Mammals Potentially Affected by the Activity

General information on the marine mammal species found in California waters can be found in Caretta et al. (2004), which is available at the following URL:​pr/​PR2/​Stock_​Assessment_​Program/​ sars.html. Refer to that document for information on these species.

The marine mammals most likely to be found in the SF-OBB area are the California sea lion, Pacific harbor seal, and harbor porpoise. From December through May gray whales may also be present in the SF-OBB area. Information on California sea lion, harbor seal, and gray whale was provided in the November 14, 2003 (68 FR 64595), Federal Register notice and is not repeated here.

Harbor Porpoise

In the eastern North Pacific, harbor porpoise are found in coastal and inland waters from Point Conception, Start Printed Page 4353California to Alaska and along at least the eastern Aleutian chain and eastern Bering Sea (Leatherwood et al., 1988). Along the west coast of the United States, harbor porpoise appear to have much less extensive home range and movement when compared to the same species in the east coast (Calambokidis and Barlow, 1991). Recent genetic analyses of harbor porpoise population structure along the eastern North Pacific indicate that there is small scale subdivision within the U.S. portion of this range (Chivers et al., 2002).

For management purposes, harbor porpoise found in off the coast of central California from San Francisco to Point Arena is treated as a separate stock (San Francisco-Russian River stock). Year-round surveys in the Gulf of the Farallones area have shown harbor porpoise occurrence within 10-20 km (6-12 miles) of San Francisco Bay (Calambokidis et al., 1990). High harbor porpoise sightings were also reported just outside the Golden Gate and about 1 km inside SFB, however, only one harbor porpoise was sighted near the vicinity of the SF-OBB site, around 100 m offshore from Yerba Buena Island on May 19, 2000 (Barrow, personal comm. 2005).

The incidental capture of harbor porpoise in California has largely been limited to set gillnet fisheries in Monterey Bay and to a lesser extent, Morro Bay. One harbor porpoise stranding inside San Francisco Bay in 1998 was attributed to fishery-related mortality, but the responsible fishery is unknown. A ban on set gillnets inshore of 60 fathoms from Point Reyes south to Point Arguello, California has been in place since September 2002.

Potential Effects on Marine Mammals and Their Habitat

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

Based on airborne noise levels measured and on-site monitoring conducted during 2004 under the previous IHA, noise levels from the East Span project did not result in the harassment of harbor seals hauled out on Yerba Buena Island (YBI). Also, noise levels from the East Span project are not expected to result in harassment of the sea lions hauled out at Pier 39 as airborne and waterborne sound pressure levels (SPLs) would attenuate to below harassment levels by the time they reach that haul-out site, 5.7 kilometers (3.5 miles) from the project site.

For reasons provided in greater detail in NMFS' November 14, 2003 (68 FR 64595) Federal Register notice and in CALTRANS' June 2004 and January 2005 annual monitoring reports, the East Span Project is resulting in only small numbers of pinnipeds being harassed (through October 2005, the biological observers indicated that only one startle behavior of a sea lion was observed as a result of East Span construction) and, therefore, is not expected to result in more than a negligible impact on marine mammal stocks and will not have a significant impact on their habitat. Short-term impacts to habitat may include minimal disturbance of the sediment where the channels are dredged for barge access and where individual bridge piers are constructed. Long-term impacts to marine mammal habitat will be limited to the footprint of the piles and the obstruction they will create following installation. However, this impact is not considered significant as the marine mammals can easily swim around the piles of the new bridge, as they currently swim around the existing bridge piers.


The following mitigation measures are currently required under the existing IHA to reduce impacts to marine mammals to the lowest extent practicable. NMFS proposes to continue these mitigation measures under a new IHA, if issued.

Barrier Systems

An air bubble curtain system is required to be used only when driving the permanent open-water piles. While the bubble curtain is required specifically as a method to reduce impacts to endangered and threatened fish species in SFB, it may also provide some benefit for marine mammals. The NMFS' Biological Opinion and the California Department of Fish and Game's (CDFG) 2001 Incidental Take Permit also allow for the use of other equally effective methods, such as cofferdams, as an alternative to the air bubble curtain system to attenuate the effects of sound pressure waves on fish during driving of permanent in-Bay piles (NMFS 2001; CDFG, 2001). Piers E-16 through E-7 for both the eastbound and westbound structures of the Skyway will be surrounded by sheet-pile cofferdams, which will be de-watered before the start of pile driving. De-watered cofferdams are generally effective sound attenuation devices. For Piers E3 through E6 of the Skyway and Piers 1 and E2 of the Self-Anchored Suspension span, it is anticipated that cofferdams will not be used; therefore, a bubble curtain will surround the piles.

Sound Attenuation

As a result of the determinations made during the Pile Installation Demonstration Project (PIDP) restrike and the investigation at the Benicia-Martinez Bridge, NMFS determined in 2003 that CALTRANS must install an air bubble curtain for pile driving for the open-water piles without cofferdams located at the SF-OBB. This air bubble curtain system consists of concentric layers of perforated aeration pipes stacked vertically and spaced no more than five vertical meters apart in all tide conditions. The minimum number of layers must be in accordance with water depth at the subject pile: 0-<5 m = 2 layers (1263 cfm); 5-<10 m = 4 layers (2526 cfm), 10-<15 m = 7 layers (4420 cfm); 15-<20 m = 10 layers (6314 cfm); 20-<25 m= 13 layers (8208 cfm). The lowest layer of perforated aeration pipes must be designed to ensure contact at all times and tidal conditions with the mudline without sinking into the bay mud. Pipes in any layer must be arranged in a geometric pattern, which will allow for the pile driving operation to be completely enclosed by bubbles for the full depth of the water column.

To provide a uniform bubble flux, each aeration pipe must have four adjacent rows of air holes along the pipe. Air holes must be 1.6-mm diameter and spaced approximately 20 mm apart. The bubble curtain system will provide a bubble flux of at least two cubic meters per minute, per linear meter of pipeline in each layer. Air holes must be placed in 4 adjacent rows.

The air bubble curtain system must be composed of the following: (1) An air compressor(s), (2) supply lines to deliver the air, (3) distribution manifolds or headers, (4) perforated aeration pipes, and (5) a frame. The frame facilitates transport and placement of the system, keeps the aeration pipes stable, and provides ballast to counteract the buoyancy of the aeration pipes in operation. Meters are required to monitor the operation of the bubble curtain system. Pressure meters will be installed and monitored at all inlets to aeration pipelines and at points of lowest pressure in each branch of the aeration pipeline. If the pressure or flow rate in any meter falls below 90 percent of its operating value, the contractor Start Printed Page 4354will cease pile driving operations until the problem is corrected and the system is tested to the satisfaction of the CALTRANS resident engineer.

Establishment of Safety/Buffer Zones

A safety zone is to be established and monitored to include all areas where the underwater SPLs are anticipated to equal or exceed 190 dB re 1 microPa RMS (impulse) for pinnipeds. Also, a 180-dB re 1 microPa RMS (impulse) safety zone for gray whales and harbor porpoises must be established for pile driving occurring during the gray whale migration season from December through May. Prior to commencement of any pile driving, a preliminary 500-m (1,640-ft) radius safety zone for pinnipeds (California sea lions and Pacific harbor seals) will be established around the pile driving site, as it was for the PIDP. Once pile driving begins, either new safety zones can be established for the 500 kJ and 1700 kJ hammers or the 500 m (1,640 ft) safety zone can be retained. If new safety zones are established based on SPL measurements, NMFS requires that each new safety zone be based on the most conservative measurement (i.e., the largest safety zone configuration). SPLs will be recorded at the 500-m (1,640-ft) contour. The safety zone radius for pinnipeds will then be enlarged or reduced, depending on the actual recorded SPLs.

Observers on boats will survey the safety zone to ensure that no marine mammals are seen within the zone before pile driving of a pile segment begins. If marine mammals are found within the safety zone, pile driving of the segment will be delayed until they move out of the area. If a marine mammal is seen above water and then dives below, the contractor will wait 15 minutes and if no marine mammals are seen by the observer in that time it will be assumed that the animal has moved beyond the safety zone. This 15-minute criterion is based on scientific evidence that harbor seals in San Francisco Bay dive for a mean time of 0.50 minutes to 3.33 minutes (Harvey and Torok, 1994), and the mean diving duration for harbor porpoises ranges from 44 to 103 seconds (Westgate et al., 1995). However, due to the limitations of monitoring from a boat, there can be no assurance that the zone will be devoid of all marine mammals at all times.

Once the pile driving of a segment begins it cannot be stopped until that segment has reached its predetermined depth due to the nature of the sediments underlying the Bay. If pile driving stops and then resumes, it would potentially have to occur for a longer time and at increased energy levels. In sum, this would simply amplify impacts to marine mammals, as they would endure potentially higher SPLs for longer periods of time. Pile segment lengths and wall thickness have been specially designed so that when work is stopped between segments (but not during a single segment), the pile tip is never resting in highly resistant sediment layers. Therefore, because of this operational situation, if seals, sea lions, or harbor porpoises enter the safety zone after pile driving of a segment has begun, pile driving will continue and marine mammal observers will monitor and record marine mammal numbers and behavior. However, if pile driving of a segment ceases for 30 minutes or more and a marine mammal is sighted within the designated safety zone prior to commencement of pile driving, the observer(s) must notify the Resident Engineer (or other authorized individual) immediately and follow the mitigation requirements as outlined previously in this document.

Soft Start

It should be recognized that although marine mammals will be protected from Level A harassment by establishment of an air-bubble curtain and marine mammal observers monitoring a 190-dB safety zone for pinipeds and 180-dB safety zone for cetaceans, mitigation may not be 100 percent effective at all times in locating marine mammals. Therefore, in order to provide additional protection to marine mammals near the project area by allowing marine mammals to vacate the area prior to receiving a potential injury, CALTRANS will also “soft start” the hammer prior to operating at full capacity. CALTRANS typically implements a “soft start” with several initial hammer strikes at less than full capacity (i.e., approximately 40-60 percent energy levels) with no less than a 1 minute interval between each strike. Similar levels of noise reduction are expected underwater. Therefore, the contractor will initiate hammering of both the 500-kJ and the 1,700-kJ hammers with this procedure in order to allow pinnipeds or cetaceans in the area to voluntarily move from the area, this should expose fewer animals to loud sounds both underwater and above water noise. This would also ensure that, although not expected, any pinnipeds and cetaceans that are missed during safety zone monitoring will not be injured.

Compliance With Equipment Noise Standards

To mitigate noise levels and, therefore, impacts to California sea lions, Pacific harbor seals, harbor porpoises, and gray whales, all construction equipment will comply as much as possible with applicable equipment noise standards of the U.S. Environmental Protection Agency, and all construction equipment will have noise control devices no less effective than those provided on the original equipment.


Since the start of the large-diameter pile driving in the Bay nearly two years ago, CALTRANS has completed pile driving of 105 piles inside cofferdams and 39 piles in open water (with the use of a bubble curtain) for a total of 144 piles. Monitoring teams were on-site for all open water pile driving and during driving of “tops” (last section of the piles, which drives the pile deeper into the substrate) inside cofferdams where underwater SPLs reached 190 dB or greater. During 70 days of monitoring, both within and outside the marine mammal safety zone, a single startle behavior from a California sea lion was observed.

The following monitoring measures are currently required under the IHA to reduce impacts to marine mammals to the lowest extent practicable. Unless, as noted, the work has been completed, NMFS proposes to continue those monitoring measures under a new IHA (if issued).

Visual Observations

The area-wide baseline monitoring and the aerial photo survey to estimate the fraction of pinnipeds that might be missed by visual monitoring have been completed under the current IHA and do not need to be continued.

Safety zone monitoring will be conducted during driving of all open-water, permanent piles without cofferdams and with cofferdams when underwater SPLs reach 190 dB RMS or greater. Monitoring of the pinniped and cetacean safety zones will be conducted by a minimum of three qualified NMFS-approved observers for each safety zone. One three-observer team will be required for the safety zones around each pile driving site, so that multiple teams will be required if pile driving is occurring at multiple locations at the same time. The observers will begin monitoring at least 30 minutes prior to startup of the pile driving. Most likely observers will conduct the monitoring from small boats, as observations from a higher vantage point (such as the SF-OBB) is not practical. Pile driving will not begin until the safety zone is clear of marine mammals. However, as described in the Mitigation section, Start Printed Page 4355once pile driving of a segment begins, operations will continue uninterrupted until the segment has reached its predetermined depth. However, if pile driving of a segment ceases for 30 minutes or more and a marine mammal is sighted within the designated safety zone prior to commencement of pile driving, the observer(s) must notify the Resident Engineer (or other authorized individual) immediately and follow the mitigation requirements as outlined previously (see Mitigation). Monitoring will continue through the pile driving period and will end approximately 30 minutes after pile driving has been completed. Biological observations will be made using binoculars during daylight hours.

In addition to monitoring from boats, during open-water pile driving, monitoring at one control site (harbor seal haul-out sites and the waters surrounding such sites not impacted by the East Span Project's pile driving activities, i.e. Mowry Slough) will be designated and monitored for comparison. Monitoring will be conducted twice a week at the control site whenever open-water pile driving is being conducted. Data on all observations will be recorded and will include items such as species, numbers, behavior, details of any observed disturbances, time of observation, location, and weather. The reactions of marine mammals will be recorded based on the following classifications that are consistent with the Richmond Bridge Harbor Seal survey methodology (for information on the Richmond Bridge authorization, see 68 FR 66076, November 25, 2003): (1) No response, (2) head alert (looks toward the source of disturbance), (3) approach water (but not leave), and (4) flush (leaves haul-out site). The number of marine mammals under each disturbance reaction will be recorded, as well as the time when seal re-haul after a flush.

Acoustical Observations

Airborne noise level measurements have been completed and underwater environmental noise levels will continue to be measured as part of the East Span Project. The purpose of the underwater sound monitoring is to establish the safety zone of 190 dB re 1 micro-Pa RMS (impulse) for pinnipeds and the safety zone of 180 dB re 1 micro-Pa RMS (impulse) for cetaceans. Monitoring will be conducted during the driving of the last half (deepest pile segment) for any given open-water pile. One pile in every other pair of pier groups will be monitored. One reference location will be established at a distance of 100 m (328 ft) from the pile driving. Sound measurements will be taken at the reference location at two depths (a depth near the mid-water column and a depth near the bottom of the water column but at least 1 m (3 ft) above the bottom) during the driving of the last half (deepest pile segment) for any given pile. Two additional in-water spot measurements will be conducted at appropriate depths (near mid-water column), generally 500 m (1,640 ft) in two directions either west, east, south or north of the pile driving site will be conducted at the same two depths as the reference location measurements. In cases where such measurements cannot be obtained due to obstruction by land mass, structures or navigational hazards, measurements will be conducted at alternate spot measurement locations. Measurements will be made at other locations either nearer or farther as necessary to establish the approximate distance for the safety zones. Each measuring system shall consist of a hydrophone with an appropriate signal conditioning connected to a sound level meter and an instrument grade digital audiotape recorder (DAT). Overall SPLs shall be measured and reported in the field in dB re 1 micro-Pa RMS (impulse). An infrared range finder will be used to determine distance from the monitoring location to the pile. The recorded data will be analyzed to determine the amplitude, time history and frequency content of the impulse.


Under the current IHA, CALTRANS has submitted weekly marine mammal monitoring reports and in January, 2005, CALTRANS submitted its Marine Mammal and Acoustic Monitoring for the Eastbound Structure. This annual report is available by contacting NMFS (see ADDRESSES) or on the Web at

Under the proposed IHA, coordination with NMFS will occur on a weekly basis, or more often as necessary. During periods with open-water pile driving activity, weekly monitoring reports will be made available to NMFS and the public at These weekly reports will include a summary of the previous week's monitoring activities and an estimate of the number of seals and sea lions that may have been disturbed as a result of pile driving activities.

In addition, CALTRANS proposes to provide NMFS' Southwest Regional Administrator with a draft final report within 90 days after completion of the westbound Skyway contract and 90 days after completion of the Suspension Span foundations contract. This report should detail the monitoring protocol, summarize the data recorded during monitoring, and estimate the number of marine mammals that may have been harassed due to pile driving. If comments are received from the Regional Administrator on the draft final report, a final report must be submitted to NMFS within 30 days thereafter. If no comments are received from NMFS, the draft final report will be considered to be the final report.

National Environmental Policy Act (NEPA)

NMFS has prepared an Environmental Assessment (EA) and made a Finding of No Significant Impact (FONSI). Therefore, preparation of an environmental impact statement on this action is not required by section 102(2) of the NEPA or its implementing regulations. A copy of the EA and FONSI are available upon request (see ADDRESSES).

Endangered Species Act (ESA)

On October 30, 2001, NMFS completed consultation under section 7 of the ESA with the Federal Highway Administration (FHWA) on the CALTRANS' construction of a replacement bridge for the East Span of the SF-OBB in California. The finding contained in the Biological Opinion was that the proposed action at the East Span of the SF-OBB is not likely to jeopardize the continued existence of listed anadromous salmonids, or result in the destruction or adverse modification of designated critical habitat for these species. Listed marine mammals are not expected to be in the area of the action and thus would not be affected. However, the proposed issuance of an IHA to CALTRANS constitutes an agency action that authorizes an activity that may affect ESA-listed species and, therefore, is subject to section 7 of the ESA. Moreover, as the effects of the activities on listed salmonids were analyzed during a formal consultation between the FHWA and NMFS, and as the underlying action has not changed from that considered in the consultation, the discussion of effects that are contained in the Biological Opinion issued to the FHWA on October 30, 2001, pertains also to this action. In conclusion, NMFS has determined that issuance of an IHA for this activity does not lead to any effects to listed species apart from those that were considered in the consultation on FHWA's action.

Preliminary Determinations

For the reasons discussed in this document and in previously identified Start Printed Page 4356supporting documents, NMFS has preliminarily determined that the impact of pile driving and other activities associated with construction of the East Span Project should result, at worst, in the Level B harassment of small numbers of California sea lions, Pacific harbor seals, harbor porpoises, and potentially gray whales that inhabit or visit SFB in general and the vicinity of the SF-OBB in particular. While behavioral modifications, including temporarily vacating the area around the construction site, may be made by these species to avoid the resultant visual and acoustic disturbance, the availability of alternate areas within SFB and haul-out sites (including pupping sites) and feeding areas within the Bay has led NMFS to preliminarily determine that this action will have a negligible impact on California sea lion, Pacific harbor seal, harbor porpoises, and gray whale populations along the California coast.

In addition, no take by Level A harassment (injury) or death is anticipated and harassment takes should be at the lowest level practicable due to incorporation of the mitigation measures mentioned previously in this document.

Proposed Authorization

NMFS proposes to issue an IHA to CALTRANS for the potential harassment of small numbers of harbor seals, California sea lions, harbor porpoises, and gray whales incidental to construction of a replacement bridge for the East Span of the San Franciso-Oakland Bay Bridge in California, provided the previously mentioned mitigation, monitoring, and reporting requirements are incorporated. NMFS has preliminarily determined that the proposed activity would result in the harassment of only small numbers of harbor seals, California sea lions, harbor porpoises, and possibly gray whales and will have no more than a negligible impact on these marine mammal stocks.

Information Solicited

NMFS requests interested persons to submit comments, information, and suggestions concerning this request (see ADDRESSES). Prior to submitting comments, NMFS recommends reviewers of this document read NMFS' November 14, 2003 Federal Register notice (68 FR 64595) on this action, especially responses to comments made previously, as NMFS does not intend to address these issues further without the submission of additional scientific information relevant to the comment.

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Dated: January 17, 2006.

Jim Lecky,

Director, Office of Protected Resources, National Marine Fisheries Service.

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[FR Doc. E6-1008 Filed 1-25-06; 8:45 am]