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Daily Rules, Proposed Rules, and Notices of the Federal Government

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XC072

Takes of Marine Mammals Incidental to Specified Activities; Marine Geophysical Survey off the Central Coast of California, November to December, 2012

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed Incidental Harassment Authorization; request for comments.
SUMMARY: NMFS has received an application from the Lamont-Doherty Earth Observatory of Columbia University (L-DEO), in cooperation with the Pacific Gas and Electric Company (PG&E), for an Incidental Harassment Authorization (IHA) to take marine mammals, by harassment, incidental to conducting a marine geophysical (seismic) survey off the central coast of California, November to December, 2012. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an IHA to L-DEO and PG&E to incidentally harass, by Level B harassment only, 25 species of marine mammals during the specified activity.
DATES: Comments and information must be received no later than October 15, 2012.
ADDRESSES: All comments received are a part of the public record and will generally be posted tohttp://www.nmfs.noaa.gov/pr/permits/incidental.htm#applicationswithout change. All Personal Identifying Information (for example, name, address, etc.) voluntarily submitted by the commenter may be publicly accessible. Do not submit confidential business information or otherwise sensitive or protected information.

A copy of the application containing a list of the references used in this document may be obtained by writing to the above address, telephoning the contact listed here (seeFOR FURTHER INFORMATION CONTACT) or visiting the internet at:http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.

The National Science Foundation (NSF), which owns the R/VMarcus G. Langseth,has prepared a draft "Environmental Assessment Pursuant to the National Environmental Policy Act, 42 U.S.C. 4321et seq.Marine Seismic Survey in the Pacific Ocean off Central California, 2012" (EA). NSF's EA incorporates a draft "Environmental Assessment of Marine Geophysical Surveys by the R/VMarcus G. Langsethfor the Central California Seismic Imaging Project," prepared by Padre Associates, Inc., on behalf of NSF, PG&E, and L-DEO, which is also available at the same internet address. Documents cited in this notice may be viewed, by appointment, during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Howard Goldstein or Jolie Harrison, Office of Protected Resources, NMFS, 301-427-8401.
SUPPLEMENTARY INFORMATION: Background

Section 101(a)(5)(D) of the MMPA, as amended (16 U.S.C. 1371(a)(5)(D)), directs the Secretary of Commerce (Secretary) to authorize, upon request, the incidental, but not intentional, taking of small numbers of marine mammals of a species or population stock, by United States citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review.

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

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

Except with respect to certain activities not pertinent here, the MMPA defines “harassment” as: Any act of pursuit, torment, or annoyance which (i) has the potential to injure a marine mammal or marine mammal stock in the wild [Level A harassment]; or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering [Level B harassment].

Summary of Request

On May 17, 2012, NMFS received an application from the L-DEO and PG&E requesting that NMFS issue an IHA for the take, by Level B harassment only, of small numbers of marine mammals incidental to conducting a marine seismic survey within the U.S. Exclusive Economic Zone off the central coast of California during November to December, 2012. NMFS received a revised application on August 31, 2012. The updated IHA application reflects revisions to the proposed project that have resulted from discussions between NMFS and the applicant during the MMPA consultation process, as well as other Federal and State regulatory requirements and include the elimination of portions of the originally planned survey area (specifically Survey Box 3) and the splitting of the proposed project into two years, and the shortening of the 2012 work window to November and December. Additionally, PG&E has agreed to operationally and financially support the design and implementation of a comprehensive monitoring, stranding response, and adaptive management plan that will support real-time decision making to reduce impacts to the Morro Bay stock of harbor porpoises (Phocoena phocoena). L-DEO and PG&E plan touse one source vessel, the R/VMarcus G. Langseth(Langseth) and a seismic airgun array to collect seismic data as part of the “Offshore Central Coastal California Seismic Imaging Project” located in the central area of San Luis Obispo County, California.

PG&E proposes to conduct a high energy seismic survey in the vicinity of the Diablo Canyon Power Plant and known offshore fault zones near the power plant. The observations will be interpreted in the context of global synthesis of observations bearing on earthquake rupture geometries, earthquake displacements, fault interactions, and fault evolution. Estimating the limits of future earthquake ruptures is becoming increasingly important as seismic hazard maps are based on geologists' maps of active faults and, locally, the Hosgri Fault strikes adjacent to one of California's major nuclear power plants. In addition to the proposed operations of the seismic airgun array and hydrophone streamer, L-DEO and PG&E intend to operate a multibeam echosounder and a sub-bottom profiler continuously throughout the survey.

Acoustic stimuli (i.e., increased underwater sound) generated during the operation of the seismic airgun array may have the potential to cause a behavioral disturbance for marine mammals in the survey area. This is the principal means of marine mammal taking associated with these activities and L-DEO and PG&E have requested an authorization to take 25 species of marine mammals by Level B harassment. Take is not expected to result from the use of the multibeam echosounder or sub-bottom profiler, for reasons discussed in this notice; nor is take expected to result from collision with the source vessel because it is a single vessel moving at a relatively slow speed (4.6 knots [kts]; 8.5 kilometers per hour [km/hr]; 5.3 miles per hour [mph]) during seismic acquisition within the survey, for a relatively short period of time (approximately 50 days). It is likely that any marine mammal would be able to avoid the vessel.

Description of the Proposed Specified Activity Project Purpose

PG&E proposes to conduct a high energy seismic survey in the vicinity of the Diablo Canyon Power Plant and known offshore fault zones near the power plant (see Figure 1 of the IHA application). The project, as proposed by L-DEO and PG&E, consists of deploying seismic or sound sources and receivers at onshore and offshore locations to generate data that can be used to improve imaging of major geologic structures and fault zones in the vicinity of the Diablo Canyon Power Plant. The details of the proposed seismic studies are outlined in a Science Plan submitted to the National Science Foundation (NSF) by L-DEO, University of Nevada, and Scripps Institution of Oceanography. NSF, as owner of theLangsethwill serve as the lead Federal agency and will ensure the approval of the proposed Science Plan is in compliance with the National Environmental Policy Act (NEPA) of 1969.

These seismic studies would provide additional insights of any relationships or connection between the known faults as well as enhance knowledge of offshore faults in proximity to the central coast of California and the Diablo Canyon Power Plant. The proposed deep penetrating (10 to 15 kilometers [km] or 6 to 9 miles [mi]), high energy seismic survey (energy greater than 2 kilo Joule) would complement a previously completed shallow (less than 1 km [0.6 mi]), low energy (less than 2 kilo Joule) three-dimensional (3D) seismic reflection survey.

The objectives of the proposed high energy 3D seismic survey are to:

• Record high resolution two-dimensional (2D) and 3D seismic reflection profiles of major geologic structures and fault zones in the vicinity of the central coast of California and Diablo Canyon Power Plant.

• Obtain high-resolution deep-imaging (greater than 1 km [0.6 mi]) of the Hosgri and Shoreline fault zones in the vicinity of the Diablo Canyon Power Plant to constrain fault geometry and slip rate (scheduled for the seismic survey activities in 2013).

• Obtain high-resolution, deep-imaging of the intersection of the Hosgri and Shoreline fault zones near Point Buchon.

• Obtain high-resolution, deep-imaging of the geometry and slip rate of the Los Osos fault, as well as the intersection of the Hosgri and Los Osos fault zones in Estero Bay.

• Augment the current regional seismic database for subsequent use and analysis through the provision of all data to the broader scientific and safety community.

The studies require the collection of data over a long period of time. However, the project timeframe is limited to fall and winter months to minimize environmental impacts to the greatest extent feasible. L-DEO and PG&E are proposing to conduct the studies 24 hours a day for 7 days a week. This schedule is designed to reduce overall air emissions, length of time for operation in the water thereby reducing impacts to marine wildlife, commercial fishing, and other area users. PG&E will work with environmental agencies to appropriately address the balancing of public health and safety and environmental concerns during the conduct of these studies.

Survey Details

The proposed survey involves both marine (offshore) and land (onshore) activities. The offshore components consist of operating a seismic survey vessel and support/monitoring vessels within the areas shown in Figure 1 of the IHA application and transiting between the four different survey box areas extending between the mouth of the Santa Maria River and Estero Bay. The seismic survey vessel would tow a series of sound-generating airguns and sound-recording hydrophones along pre-determined shore parallel and shore-perpendicular transects to conduct deep (10 to 15 km [6 to 9 mi]) seismic reflection profiling of major geologic structures and fault zones in the vicinity of the Diablo Canyon Power Plant.

The offshore part of the survey activities include the placement of a limited number of seafloor geophones (e.g., Fairfield Z700 nodal units) into nearshore waters.

The planned seismic survey (e.g., equipment testing, startup, line changes, repeat coverage of any areas, and equipment recovery) will consist of approximately 3,565.8 km (1,925.4 nmi) (1,417.6 km [765.4 nmi] for Survey Box 4 and 2,148.2 km [1,159.9 nmi] for Survey Box 2) of transect lines (including turns) in the survey area off the central coast of California (see Figure 2 of the IHA application). In addition to the operations of the airgun array, a Kongsberg EM 122 multibeam echosounder and Knudsen Chirp 3260 sub-bottom profiler will also be operated from theLangsethcontinuously throughout the cruise. There will be additional seismic operations associated with equipment testing, ramp-up, and possible line changes or repeat coverage of any areas where initial data quality is sub-standard. In L-DEO and PG&E's estimated take calculations, 25% has been added for those additional operations. Detailed descriptions of the proposed actions for each component are provided below in this document.

Vessel Movements

The tracklines for the 3D seismic survey will encompass an area ofapproximately 740.52 km2(215.9 square nautical miles [nmi2]). The 2012 project area is divided into two “primary target areas” (Survey Boxes 2 and 4) are described below and shown in Figure 2 of the IHA application. The offshore (vessel) survey would be conducted in both Federal and State waters and water depths within the proposed survey areas ranging from 0 to over 400 m (1,300 ft). The State Three-Mile Limit is identified in Figure 1 of the IHA application. The Point Buchon Marine Protected Area lies within portions of the survey area. In addition, the Monterey Bay National Marine Sanctuary, a Federally-protected marine sanctuary that extends northward from Cambria to Marine County, is located to the north and outside of the proposed project area.

Survey Box 2 (Survey area from Estero Bay to offshore Santa Maria River Mouth):

• Area: 406.04 km2(118.4 nmi2);

• Total survey line length is 2,148.2 km (1,159.9 nmi); and

• Strike line surveys along the Hosgri fault zone and Shoreline, Hosgri, and Los Osos fault intersections.

Survey Box 4 (Estero Bay):

• Area: 334.48 km2(97.5 nmi2);

• Total survey line length is 1,417.6 km (765.4 nmi);

• Dip line survey across the Hosgri and Los Osos fault zones in Estero Bay.

Figure 2 of the IHA application depicts the proposed survey transit lines. These lines depict the survey lines as well as the turning legs. The full seismic array is firing during the straight portions of the track lines as well as the initial portions of the run-out (offshore) sections and later portions of the run-in (inshore) sections. During turns and most of the initial portion of the run-ins, there will only be one airgun firing (i.e., mitigation airgun). Assuming a daily survey rate of approximately 8.3 km/hour (km/hr) (4.5 knots [kts] for 24/7 operations), the Survey Box 2 is expected to take approximately 14 days and approximately 9.25 days for Survey Box 4. When considering mobilization, demobilization, refueling, equipment maintenance, weather, marine mammal activity, and other contingencies, the proposed survey is expected to be completed in 49.25 days.

Mobilization and Demobilization

The offshore equipment and vessels for the proposed 3D marine seismic survey are highly specialized and typically no seismic vessels are located in California. The proposed seismic survey vessel (R/VMarcus G. Langseth) is currently operating on the U.S. west coast and is available to conduct the proposed seismic survey work.

TheLangsethwould transit south prior to the start of survey operations (approximately October 15 through December 31, 2012, with active airgun survey operations starting approximately November 1, 2012). Once the vessel has arrived in the project area, the survey crew, any required equipment, and support provisions would be transferred to the vessel. Larger equipment, if required, would need to be loaded onboard the vessel at either Port of San Francisco/Oakland or Port Hueneme. The proposed survey vessel is supported by two chase/scout boats, each with three Protected Species Observers (PSOs) and a third support boat that will provide logistical support to theLangsethor chase boats. This support vessel will also serve as a relief vessel for either of the two chase boats as required or equivalent. Any additional scout/monitoring vessels required for the proposed project will be drawn from local vessel operators. Upon completion of the offshore survey operations, the survey crew would be transferred to shore and the survey vessel would transit out to the proposed project area.

Nearshore operations would be conducted using locally available vessels such as the M/VMichael Uhl(Michael Uhl) or equivalent vessel. Equipment, including the geophones and cables, would be loaded aboard theMichael Uhlin Morro Bay Harbor and transferred to the offshore deployment locations. Following deployment and recovery of the geophones and cables, they would be transferred back to Morro Bay Harbor for transport offsite.

During onshore operations, receiver line equipment would be deployed by foot-based crews supported by four-wheel drive vehicles or small vessel. Once the proposed project has been completed, the equipment would demobilize from the area by truck.

Offshore Survey Operations

The proposed offshore seismic survey would be conducted with vessels specifically designed and built to conduct such surveys. PG&E has selected theLangseth,which is operated by L-DEO. The following outlines the general specifications for theLangsethand the support vessels needed to complete the proposed offshore seismic survey.

In water depths from 30 to 305 m (100 to greater than 1,000 ft), theLangsethwill tow four hydrophone streamers with a length of approximately 6 km (3.2 nmi). The intended tow depth of the streamers is approximately 9 m (29.5 ft). Flotation is provided on each streamer as well as streamer recovery devices. The streamer recovery devices are activated when the streamer sinks to a pre-determined depth (e.g., 50 m [164 ft]) to aid in recovery.

• Primary vessel—theLangsethis 71.5 m (235 ft) in length, and is outfitted to deploy/retrieve hydrophone streamers and airgun array, air compressors for the airgun array, and survey recording facilities.

• Two Chase/Scout boats—22.9 to 41.2 m (75 to 135 ft) in length and will be around theLangsethto observe potential obstructions, conduct additional marine mammal monitoring and support deployment of seismic equipment.

• Third support vessel-will be approximately 18.3 to 25.9 m (60 to 85 ft) in length and would act as a support boat for theLangsethand the two other chase/scout and would provide relief to either chase/scout boat as required.

• A nearshore work vessel (e.g.,Michael Uhl) approximately 50 m (150 ft) in length would be used to deploy and retrieve seafloor geophones in the shallow water (0 to 20 m) zone.

• Monitoring aircraft—Partenavia P68-OBS “Observer,” a high-wing, twin-engine plane or equivalent aircraft is 9.5 m (31 ft) in length and has a wingspan of 12 m (39 ft) with a carrying capacity of six persons. The aircraft has two “bubble” observation windows, a glass nose for clear observation, and will be equipped with communication and safety equipment sufficient to support the proposed operations. The aircraft would be used to perform aerial surveys of marine mammals.

Vessel Specifications

TheLangseth,a seismic research vessel owned by the NSF, will tow the 36 airgun array, as well as the hydrophone streamer, along predetermined lines (see Figure 2 of the IHA application). When theLangsethis towing the airgun array and the hydrophone streamer, the turning rate of the vessel is limited to three degrees per minute (2.5 km [1.5 mi]). Thus, the maneuverability of the vessel is limited during operations with the streamer. The vessel would “fly” the appropriate U.S. Coast Guard-approved day shapes (mast head signals used to communicate with other vessels) and display the appropriate lighting to designate the vessel has limited maneuverability.

The vessel has a length of 71.5 m (235 ft); a beam of 17.0 m (56 ft); a maximum draft of 5.9 m (19 ft); and a gross tonnage of 3,834. TheLangsethwas designed as a seismic research vessel with a propulsion system designed to be as quiet as possible to avoid interference with the seismic signals emanating fromthe airgun array. The ship is powered by two 3,550 horsepower (hp) Bergen BRG-6 diesel engines which drive two propellers directly. Each propeller has four blades and the shaft typically rotates at 750 revolutions per minute. The vessel also has an 800 hp bowthruster, which is not used during seismic acquisition. TheLangseth's operation speed during seismic acquisition is typically 7.4 to 9.3 km per hour (hr) (km/hr) (4 to 5 knots [kts]). When not towing seismic survey gear, theLangsethtypically cruises at 18.5 km/hr (10 kts). TheLangsethhas a range of 25,000 km (13,499 nmi) (the distance the vessel can travel without refueling).

The vessel also has an observation tower from which Protected Species Visual Observers (PSVO) will watch for marine mammals before and during the proposed airgun operations. When stationed on the observation platform, the PSVO's eye level will be approximately 21.5 m (71 ft) above sea level providing the PSVO an unobstructed view around the entire vessel. More details of theLangsethcan be found in the IHA application.

Acoustic Source Specifications Seismic Airguns

TheLangsethwill deploy a 36-airgun array, consisting of two 18 airgun sub-arrays. Each sub-array will have a volume of approximately 3,300 cubic inches (in3). The airgun array will consist of a mixture of Bolt 1500LL and Bolt 1900LLX airguns ranging in size from 40 to 360 in3, with a firing pressure of 1,900 pounds per square inch (psi). The 18 airgun sub-arrays will be configured as two identical linear arrays or “strings” (see Figure 3 and 4 of the IHA application). Each string will have 10 airguns, the first and last airguns in the strings are spaced 16 m (52.5 ft) apart. Of the 10 airguns, nine airguns in each string will be fired simultaneously (1,650 in3), whereas the tenth is kept in reserve as a spare, to be turned on in case of failure of another airgun. The sub-arrays would be fired alternately during the survey. The two airgun sub-arrays will be distributed across an area of approximately 12 x 16 m (40 x 52.5 ft) behind theLangsethand will be towed approximately 140 m (459.3 ft) behind the vessel. Discharge intervals depend on both the ship's speed and Two Way Travel Time recording intervals. The shot interval will be 37.5 m (123) during the study. The shot interval will be relatively short, approximately 15 to 20 seconds (s) based on an assumed boat speed of 4.5 knots. During firing, a brief (approximately 0.1 s) pulse sound is emitted; the airguns will be silent during the intervening periods. The dominant frequency components range from two to 188 Hertz (Hz).

The tow depth of the airgun array will be 9 m (29.5 ft) during the surveys. Because the actual source is a distributed sound source (18 airguns) rather than a single point source, the highest sound measurable at any location in the water will be less than the nominal source level. In addition, the effective source level for sound propagating in near-horizontal directions will be substantially lower than the nominal omni-directional source level applicable to downward propagation because of the directional nature of the sound from the airgun array (i.e., sound is directed downward). Figure 3 of the IHA application shows one linear airgun array or “string” with ten airguns. Figure 4 of the IHA application diagrams the airgun array and streamer deployment from theLangseth.

Hydrophone Streamer

Acoustic signals will be recorded using a system array of four hydrophone streamers, which would be towed behind theLangseth.Each streamer would consist of Sentry Solid Streamer Sercel cable approximately 6 km (3.2 nmi) long. The streamers are attached by floats to a diverter cable, which keeps the streamer spacing at approximately 100 to 150 m (328 to 492 ft) apart.

Seven hydrophones will be present along each streamer for acoustic measurement. The hydrophones will consist of a mixture of Sonardyne Transceivers. Each streamer will contain three groups of paired hydrophones, with each group approximately 2,375 m (7,800 ft) apart. The hydrophones within each group will be approximately 300 m (984 ft) apart. One additional hydrophone will be located on the tail buoy attached to the end of the streamer cable. In addition, one Sonardyne Transducer will be attached to the airgun array. Compass birds will be used to keep the streamer cables and hydrophones at a depth of approximately 10 m (32.8 ft). One compass bird will be placed at the front end of each streamer as well as periodically along the streamer. Figure 4 of the IHA application depicts the configuration of both the streamer and airgun array used by theLangseth.Details regarding the hydrophone streamer and acoustic recording equipment specifications are included in Table 1 of the IHA application.

Metrics Used in This Document

This section includes a brief explanation of the sound measurements frequently used in the discussions of acoustic effects in this document. Sound pressure is the sound force per unit area, and is usually measured in micropascals (μPa), where 1 pascal (Pa) is the pressure resulting from a force of one newton exerted over an area of one square meter. Sound pressure level (SPL) is expressed as the ratio of a measured sound pressure and a reference level. The commonly used reference pressure level in underwater acoustics is 1 μPa, and the units for SPLs are dB re: 1 μPa. SPL (in decibels [dB]) = 20 log (pressure/reference pressure).

SPL is an instantaneous measurement and can be expressed as the peak, the peak-peak (p-p), or the root mean square (rms). Root mean square, which is the square root of the arithmetic average of the squared instantaneous pressure values, is typically used in discussions of the effects of sounds on vertebrates and all references to SPL in this document refer to the root mean square unless otherwise noted. SPL does not take the duration of a sound into account.

Characteristics of the Airgun Pulses

Airguns function by venting high-pressure air into the water which creates an air bubble. The pressure signature of an individual airgun consists of a sharp rise and then fall in pressure, followed by several positive and negative pressure excursions caused by the oscillation of the resulting air bubble. The oscillation of the air bubble transmits sounds downward through the seafloor and the amount of sound transmitted in the near horizontal directions is reduced. However, the airgun array also emits sounds that travel horizontally toward non-target areas.

The nominal source levels of the airgun arrays used by L-DEO and PG&E on theLangsethare 236 to 265 dB re 1 μPa (p-p) and the rms value for a given airgun pulse is typically 16 dB re 1 μPa lower than the peak-to-peak value (Greene, 1997; McCauleyet al.,1998, 2000a). The specific source output for the 18 airgun array is 252 dB (peak) and 259 dB (p-p). However, the difference between rms and peak or peak-to-peak values for a given pulse depends on the frequency content and duration of the pulse, among other factors.

Accordingly, L-DEO and PG&E have predicted the received sound levels in relation to distance and direction from the 18 airgun array and the single Bolt1900LL 40 in3airgun, which will be used during power-downs. A detailed description of L-DEO and PG&E's modeling for this survey's marine seismic source arrays for protected species mitigation is provided in Appendix A of the IHA application and NSF's EA. Appendix A (GSI Technical Memorandum 470-3 and GSI Technical Memorandum 470-2RevB) of the IHA application and NSF's EA discusses the characteristics of the airgun pulses. NMFS refers the reviewers to the IHA application and EA documents for additional information.

Predicted Sound Levels for the Airguns

To determine exclusion zones for the airgun array to be used off the central coast of California, the noise modeling for the proposed 3D seismic survey is based on the results of mathematical modeling conducted by Greeneridge Sciences, Inc. (2011). The model results are based upon the airgun specifications provided for theLangsethand seafloor characteristics available for the project area. Specifically, L-DEO's predicted sound contours were used to estimate pulse sound level extrapolated to an effective distance of one meter, effectively reducing the multi-element array to a point source. Such a description is valid for descriptions of the far field sounds, i.e., at distances that are long compared to the dimensions of the array and the sound wavelength. Greeneridge Sciences, Inc. did not account for near-field effects. However, since the vast majority of acoustic energy radiated by an airgun array is below 500 Hz and the near field is small for the given airgun array at these frequencies (the radius of the near field around the array is 21 m [68.9 ft] or less for frequencies below 500 Hz), near-field effects are considered minimal.

The sound propagation from the airgun array was modeled in accordance with physical description of sound propagation and depends on waveguide characteristics, including water depth, water column sound velocity profile, and geoacoustic parameters of the ocean bottom. For the sound propagation model, Greeneridge Sciences, Inc. relied on variants of the U.S. Navy's range-dependent Acoustic Model. Greeneridge Sciences, Inc. modeled three 2D (range versus depth) propagation paths, each with range-dependent (i.e., range-varying) bathymetry and range-independent geoacoustic profiles. The resulting received sound levels at a receiver depth of 6 m (19.7 ft) and across range were then “smoothed” via least-squares regression. The monotonically-decreasing regression equations yielded the estimated safety radii.

The accuracy of the sound field predicted by the acoustic propagation model is limited by the quality and resolution of the available environmental data. Greeneridge Sciences, Inc. used environmental information provided by the client for the proposed survey area, specifically, bathymetry data, a series of measured water column sound speed profiles, and descriptive sediment and basement properties. Greeneridge Sciences, Inc. used two geoacoustic profiles for its three propagation paths: One for the upslope propagation path (sand overlaying sandstone) and one for the downslope and alongshore propagation paths (silt overlaying sandstone)

L-DEO and PG&E have used these calculated values to determine exclusion zones for the 18 airgun array and previously modeled measurements by L-DEO for the single airgun, to designate exclusion zones for purposes of mitigation, and to estimate take for marine mammals off the central coast of California. A detailed description of the modeling effort is provided in Appendix A of NSF's EA.

Using the model (airgun array and single airgun), Table 1 (below) shows the distances at which three rms sound levels are expected to be received from the 18 airgun array and a single airgun. To avoid the potential for injury or permanent physiological damage (Level A harassment), NMFS (1995, 2000) has concluded that cetaceans and pinnipeds should not be exposed to pulsed underwater noise at received levels exceeding 180 dB re: 1 µPa and 190 dB re: 1 µPa, respectively. L-DEO and PG&E used these levels to establish the exclusion zones. If marine mammals are detected within or about to enter the appropriate exclusion zone, the airguns will be powered-down (or shut-down, if necessary) immediately. NMFS also assumes that marine mammals exposed to levels exceeding 160 dB re: 1 µPa may experience Level B harassment.

Table 1 summarizes the predicted distances at which sound levels (160, 180, and 190 dB [rms]) are expected to be received from the 18 airgun array and a single airgun operating in upslope (inshore), downslope (offshore), and alongshore depths. For the proposed project, L-DEO and PG&E plan to use the upslope distance (inshore) for the 160 dB (6,210 m [20,374 ft]) and 180 dB (1,010 m [3,313.7 ft], and alongshore distance for the 190 dB (320 m [1,049.9 ft]), for the determination of the buffer and exclusion zones since this represents the largest and therefore most conservative distances determined by the Greeneridge Sciences, Inc. modeling.

Table 1. Modeled (array) or predicted (single airgun) distances to which sound levels ≥ 190, 180, and 160 dB re: 1 μPa (rms) could be received in upslope, downslope, and alongshore propagation paths during the proposed survey off the central coast of California, November to December, 2012.

Sound pressure level
  • (SPL) (dB re 1 µPa)
  • Predicted RMS radii distances for 18 airgun array Upslope distance
  • (inshore)
  • Downslope distance
  • (offshore)
  • Alongshore distance
    190 dB 250 m (0.13 nmi) 280 m (0.15 nmi) 320 m (0.17 nmi) 180 dB 1,010 m (0.55 nmi) 700 m (0.38 nmi) 750 m (0.40 nmi) 160 dB 6,210 m (3.35 nmi) 4,450 m (2.40 nmi) 4,100 m (2.21 nmi)
    Sound pressure level
  • (SPL) (dB re 1 µPa)
  • Predicted RMS radii distances for single airgun Shallow water
  • (< 100 m)
  • Intermediate water
  • (100 to 1,000 m)
  • Deep Water
  • (> 1,000 m)
  • 190 dB 150 m (0.08 nmi) 18 m (< 0.01 nmi) 12 m (< 0.01 nmi) 180 dB 296 m (0.16 nmi) 60 m (0.03 nmi) 40 m (0.02 nmi) 160 dB 1,050 m (0.57 nmi) 578 m (0.31 nmi) 385 m (0.21 nmi)

    Along with the airgun operations, two additional acoustical data acquisition systems will be operated from theLangsethcontinuously during the survey. The ocean floor will be mapped with the Kongsberg EM 122 multibeam echosounder and a Knudsen 320B sub-bottom profiler. These sound sources will be operated continuously from theLangseththroughout the cruise.

    Multibeam Echosounder

    TheLangsethwill operate a Kongsberg EM 122 multibeam echosounder concurrently during airgun operations to map characteristics of the ocean floor. The hull-mounted multibeam echosounder emits brief pulses of sound (also called a ping) (10.5 to 13, usually 12 kHz) in a fan-shaped beam that extends downward and to the sides of the ship. The transmitting beamwidth is 1° or 2° fore-aft and 150° athwartship and the maximum source level is 242 dB re: 1 μPa.

    Each ping consists of eight (in water greater than 1,000 m) or four (less than 1,000 m) successive, fan-shaped transmissions, each ensonifying a sector that extends 1° fore-aft. Continuous-wave pulses increase from 2 to 15 milliseconds (ms) long in water depths up to 2,600 m (8,350.2 ft), and frequency modulated (FM) chirp pulses up to 100 ms long are used in water greater than 2,600 m. The successive transmissions span an overall cross-track angular extent of about 150°, with 2 ms gaps between the pulses for successive sectors (see Table 2 of the IHA application).

    Sub-Bottom Profiler

    TheLangsethwill also operate a Knudsen Chirp 320B sub-bottom continuously throughout the cruise simultaneously with the multibeam echosounder to map and provide information about the sedimentary features and bottom topography. The beam is transmitted as a 27° cone, which is directed downward by a 3.5 kHz transducer in the hull of theLangseth.The maximum output is 1 kilowatt (kW), but in practice, the output varies with water depth. The pulse interval is one second, but a common mode of operation is to broadcast five pulses at one second intervals followed by a 5-second pause.

    Both the multibeam echosounder and sub-bottom profiler are operated continuously during survey operations. Given the relatively shallow water depths of the survey area (20 to 300 m [66 to 984 ft]), the number of pings or transmissions would be reduced from 8 to 4, and the pulse durations would be reduced from 100 ms to 2 to 15 ms for the multibeam echosounder. Power levels of both instruments would be reduced from maximum levels to account for water depth. Actual operating parameters will be established at the time of the survey.

    NMFS expects that acoustic stimuli resulting from the proposed operation of the single airgun or the 18 airgun array has the potential to harass marine mammals. NMFS does not expect that the movement of theLangseth,during the conduct of the seismic survey, has the potential to harass marine mammals because of the relatively slow operation speed of the vessel (approximately 4.6 knots [kts]; 8.5 km/hr; 5.3 mph) during seismic acquisition.

    Gravimeter

    TheLangsethwill employ a Bell Aerospace BGM-3 gravimeter system (see Figure 5 of the IHA application) to measure very tiny fractional changes within the Earth's gravity caused by nearby geologic structures, the shape of the Earth, and by temporal tidal variations. The gravimeter has been specifically designed to make precision measurements in a high motion environment. Precision gravity measurements are attained by the use of the highly accurate Bell Aerospace Model XI inertial grade accelerometer.

    Magnetometer

    TheLangsethwill employ a Bell Aerospace BGM-3 geometer, which contains a model G-882 cesium-vapor marine magnetometer (see Figure 6 of the IHA application). Magnetometers measure the strength and/or direction of a magnetic field, generally in units of nanotesla in order to detect and map geologic formations. These data would enhance earlier marine magnetic mapping conducted by the U.S. Geologic Survey (Sliteret al.,2009).

    The G-882 is designed for operation from small vessels for shallow water surveys as well as for the large survey vessels for deep tow applications. Power may be supplied from a 24 to 30 VDC battery power or a 110/220 VAC power supply. The standard G-882 tow cable includes a Vectran strength member and can be built to up to 700 m (2,297 ft) (no telemetry required). The shipboard end of the tow cable is attached to a junction box or onboard cable. Output data are recorded on a computer with an RS-232 serial port.

    Both the gravimeter and magnetometers are “passive” instruments and do not emit sounds, impulses, or signals, and are not expected to affect marine mammals.

    Nearshore and Onshore Survey Operations

    To collect deep seismic data in water depths that are not accessible by theLangseth(less than 25 m [82 ft]), seafloor geophones and both offshore and onshore seismic sources will be used. The currently proposed locations for the seafloor geophone lines between Point Buchon and Point San Luis are shown in Figure 7 of the IHA application.

    Twelve Fairfield Z700 marine nodes would be placed on the seafloor along two nearshore survey routes as a pilot test prior to the full deployment of 600 nodes scheduled for 2013. The northern route (Crowbar Beach) traverses the Point Buchon MPA north of Diablo Canyon Power Plant. The southern route (either Green Peak or Deer Canyon) is located south of the Diablo Canyon Power Plant. The approximate locations of the proposed nodal routes are depicted in Figure 7 of the IHA application. Six nodes would be placed at 500 m (1,640.4 ft) intervals along each route for a total length of 3 km (1.9 mi). Maximum water depth ranges from 70 m (229.7 ft) (Crowbar) to 30 m (98.4 ft) (Deer Canyon). Marine nodes would be deployed using a vessel and (in some locations) divers and will be equipped with ultra-short baseline acoustic tracking system to position and facilitate recovery of each node. The tracking equipment will be used to provide underwater positioning of a remotely operated vehicle during deployment and recovery of the nodes.

    The seafloor equipment will be in place for the duration of the data collection for the offshore 3D high energy seismic surveys plus deployment and recovery time. Node deployment will be closely coordinated with both offshore and onshore survey operations to ensure survey activities are completed before the projected batter life of 45 days is exceeded. PG&E anticipates using a locally-available vessel to deploy and retrieve the geophones. The vessel would be a maximum of 50 m in length. TheMichael Uhl,which is locally available, its sister vessel, or a vessel of similar size and engine specification, is proposed for this purpose.

    Onshore, a linear array of ZL and nodals will be deployed along a single route on the Morro Strand to record onshore sound transmitted from the offshore airgun surveys. Route location is shown in Figure 9 of the IHA application. Ninety nodes would be placed at 100 m (328 ft) intervals along the strand for a total route length of approximately 9 km (5.6 mi). Theautonomous, nodal, cable-less recording devices (see Figure 9 of the IHA application) would be deployed by foot into the soil adjacent to existing roads, trails, and beaches. The nodal systems are carried in backpacks and pressed into the ground at each receiver point. Each nodal would be removed following completion of the data collection. PG&E estimates that the onshore receiver activities would be conducted over a 2 to 3 day period, concurrent with the offshore surveys. The onshore receivers would record the offshore sound sources during the seismic operations. Figure 10 of the IHA application depicts the area where the onshore receivers are proposed to be placed along the Morro Strand. PG&E and NMFS have determined that onshore activities are unlikely to impact marine mammals, including pinnipeds at haul-outs and rookeries, in the proposed action area.

    More information on the vessels, equipment, and personnel requirements proposed for use in the offshore survey can be found in sections 1.4 and 1.5 of the IHA application.

    Dates, Duration, and Specified Geographic Region

    The proposed project located offshore of central California would have a total duration of approximately 49.25 operational days occurring during the November through December, 2012 timeframe, which will include approximately 24 days of active seismic airgun operations. Mobilization will initiate on October 15, 2012, with active airgun surveys taking place from November 1 through December 31, 2012. Below is an estimated schedule for the proposed project based on the use of theLangsethas the primary survey vessel (the total number of days is based on adding the non-concurrent tasks):

    • Mobilization to project site—6 days;

    • Initial equipment deployment—3 days (includes offshore geophone deployment);

    • Pre-activity marine mammal surveys—5 days (concurrent with offshore deployment activities);

    • Onshore geophone deployment—2 to 3 days (concurrent with offshore deployment activities);

    • Equipment calibration and sound check (i.e., sound source verification)—5 days;

    • Seismic survey—23.25 days (Survey Box 4 will be surveyed first followed by Survey Box 2, 24/7 operations in all areas);

    • Survey Box 4 (survey area within Estero Bay)—9.25 days;

    • Survey Box 2 (survey area from Estero Bay to offshore to the mouth of the Santa Maria River)—14 days;

    • Streamer and airgun preventative maintenance—2 days;

    • Additional shut-downs (marine mammal presence, crew changes, and unanticipated weather delays)—4 days;

    • Demobilization—6 days.

    Placement of the onshore receiver lines would be completed prior to the start of offshore survey activities and would remain in place until the offshore survey can be completed. Some minor deviation from this schedule is possible, depending on logistics and weather (i.e., the cruise may depart earlier or be extended due to poor weather; there could be additional days of seismic operations if collected data are deemed to be of substandard quality).

    The latitude and longitude for the bounds of the two survey boxes are:

    Survey Box 4: 35° 25′ 21.7128″ North, 120° 57′ 44.7001″ West 35° 20′ 16.0648″ North, 121° 9′ 24.1914″ West 35° 18′ 38.3096″ North, 120° 53′ 29.9525″ West 35° 14′ 42.003″ North, 121° 3′ 36.9513″ West Survey Box 2: 34° 57′ 43.3388″ North, 120° 45′ 12.8318″ West 34° 55′ 40.383″ North, 120° 48′ 59.3101″ West 35° 25′ 40.62″ North, 121° 00′ 27.12″ West 35° 23′ 57.26″ North, 121° 04′ 37.28″ West Description of the Marine Mammals in the Area of the Proposed Specified Activity

    Thirty-six marine mammal species (29 cetaceans [whales, dolphins, and porpoises], 6 pinnipeds [seals and sea lions], and 1 fissiped) are known to or could occur off the central coast of California study area. Several of these species are listed as endangered under the U.S. Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531et seq.), including the North Pacific right (Eubalaena japonica), humpback (Megaptera novaeangliae), sei (Balaenoptera borealis), fin (Balaenoptera physalus), blue (Balaenoptera musculus), and sperm (Physeter macrocephalus) whales. The Guadalupe fur seal (Arctocephalus townsendi) and Eastern stock of Steller sea lion (Eumetopias jubatus), and southern sea otter (Enhydra lutris nereis) are listed as threatened under the ESA. The southern sea otter is the one marine mammal species mentioned in this document that is managed by the U.S. Fish and Wildlife Service (USFWS) and is not considered further in this analysis; all others are managed by NMFS. While in their range, North Pacific right, sei, and sperm whale sightings are uncommon in the proposed project area, and have a low likelihood of occurrence during the proposed seismic survey. Similarly, the proposed project area is generally north of the range of the Guadalupe fur seal. Table 2 (below) presents information on the abundance, distribution, population status, conservation status, and population trend of the species of marine mammals that may occur in the proposed study area during November to December, 2012.

    Table 2. The habitat, regional abundance, and conservation status of marine mammals that may occur in or near the proposed seismic survey area off the central coast of California. (See text and Table 4 in L-DEO and PG&E's application for further details.)

    Species Habitat Population estimate3(minimum) ESA1 MMPA2 Population trend3 Mysticetes: North Pacific right whale (Eubalaena japonica) Pelagic and coastal NA (18 to 21)—Eastern North Pacific stock EN D No information available Gray whale (Eschrichtius robustus) Coastal, shallow shelf 19,126 (18,017)—Eastern North Pacific stock DL—Eastern North Pacific stock EN—Western North Pacific stock NC—Eastern North Pacific stock D—Western North Pacific stock Increasing over past several decades Humpback whale (Megaptera novaeangliae) Mainly nearshore, banks 2,043 (1,878)—California/Oregon/Washington stock EN D Increasing Minke whale (Balaenoptera acutorostrata) Pelagic and coastal 478 (202)—California/Oregon/Washington stock NL NC No information available Sei whale (Balaenoptera borealis) Primarily offshore, pelagic 126 (83)—Eastern North Pacific stock EN D No information available Fin whale (Balaenoptera physalus) Continental slope, pelagic 3,044 (2,624)—California/Oregon/Washington stock EN D Unable to determine Blue whale (Balaenoptera musculus) Pelagic, shelf, coastal 2,497 (2,046)—Eastern North Pacific stock EN D Unable to determine Odontocetes: Sperm whale (Physeter macrocephalus) Pelagic, deep sea 971 (751)—California/Oregon/Washington stock EN D Variable Pygmy sperm whale (Kogia breviceps) Deep waters off the shelf 579 (271)—California/Oregon/Washington stock NL NC No information available Dwarf sperm whale (Kogia sima) Deep waters off the shelf NA—California/Oregon/Washington stock NL NC No information available Cuvier's beaked whale (Ziphius cavirostris) Pelagic 2,143 (1,298)—California/Oregon/Washington stock NL NC No information available Baird's beaked whale (Berardius bairdii) Pelagic 907 (615)—California/Oregon/Washington stock NL NC No information available Mesoplodonbeaked whale (includes Blainville's beaked whale [M. densirostris], Perrin's beaked whale [M. perrini], Lesser beaked whale [M. peruvianis], Stejneger's beaked whale [M. stejnegeri], Gingko-toothed beaked whale [M. gingkodens], Hubbs' beaked whale [M. carlhubbsi]) Pelagic 1,204 (576)—California/Oregon/Washington stock NL NC No information available Bottlenose dolphin (Tursiops truncatus) Coastal, oceanic, shelf break 1,006 (684)—California/Oregon/Washington stock 323 (290)—California Coastal stock NL NC D—Western North Atlantic coastal No information available Stable Striped dolphin (Stenella coeruleoalba) Off continental shelf 10,908 (8,231)—California/Oregon/Washington stock NL NC Unable to determine Short-beaked common dolphin (Delphinus delphis) Shelf, pelagic, seamounts 411,211 (343,990)—California/Oregon/Washington stock NL NC Variable with oceanographic conditions Long-beaked common dolphin (Delphinus capensis) Coastal, on continental shelf 27,046 (17,127)—California stock NL NC No information available, variable with oceanographic conditions Pacific white-sided dolphin (Lagenorhynchus obliquidens) Offshore, slope 26,930 (21,406)—California/Oregon/Washington stock NL NC No information available Northern right whale dolphin (Lissodelphis borealis) Slope, offshore waters 8,334 (6,019)—California/Oregon/Washington stock NL NC Unable to determine Risso's dolphin (Grampus griseus) Deep water, seamounts 6,272 (4,913)—California/Oregon/Washington stock NL NC Unable to determine Killer whale (Orcinus orca) Pelagic, shelf, coastal 240 (162)—Eastern North Pacific Offshore stock 346 (346)—Eastern North Pacific Transient stock 354 (354)—West Coast Transient stock NL EN—Southern resident NC D—Southern resident, AT1 transient No information available, No information available, Declining, Increased and slowing Short-finned pilot whale (Globicephala macrorhynchus) Pelagic, shelf coastal 760 (465)—California/Oregon/Washington stock NL NC Unable to determine Harbor porpoise (Phocoena phocoena) Coastal and inland waters 2,044 (1,478)—Morro Bay stock NL NC Increasing Dall's porpoise (Phocoenoides dalli) Shelf, slope, offshore 42,000 (32,106)—California/Oregon/Washington stock NL NC No information available Pinnipeds: California sea lion (Zalophus californianus) Coastal, shelf 296,750 (153,337)—U.S. stock NL NC Increasing Steller sea lion (Eumetopias jubatus) Coastal, shelf 49,685 (42,366)—Western stock 58,334 to 72,223 (52,847)—Eastern stock T D Decreasing in California Guadalupe fur seal (Arctocephalus townsendi) Coastal, shelf 7,408 (3,028)—Mexico stock T D Increasing Northern fur seal (Callorhinus ursinus) Pelagic, offshore 9,968 (5,395)—San Miguel Island stock NL D Increasing Northern elephant seal (Mirounga angustirostris) Coastal, pelagic in migration 124,000 (74,913)—California Breeding stock NL NC Increasing Pacific harbor seal (Phoca vitulina richardsi) Coastal 30,196 (26,667)—California stock NL NC Increasing Fissipeds: Southern sea otter (Enhydra lutris nereis) Coastal 2,711—California stock T D Increasing NA = Not available or not assessed. 1U.S. Endangered Species Act: EN = Endangered, T = Threatened, DL = Delisted, NL = Not listed. 2U.S. Marine Mammal Protection Act: D = Depleted, NC = Not Classified. 3NMFS Stock Assessment Reports.

    In the Pacific Ocean, harbor porpoises are found in coastal and inland waters from California to Alaska and across to Kamchatka and Japan (Gakin, 1984). Harbor porpoises appear to have more restricted movements along the western coast of the continental United States, than along the eastern coast, with some regional differences within California. Based on genetic differences that showed small-scale subdivision within the U.S. portion of its range, California coast stocks were re-evaluated and the stock boundaries were revised. The boundaries (i.e., range) for the Morro Bay stock of harbor porpoises are from Point Sur to Point Conception, California. The vast majority of harbor porpoise in California are within the 0 to 92 m (0 to 301.8 ft) depth, however, a smaller percentage can be found between the 100 to 200 m (328 to 656.2 ft) isobaths. A systematic ship survey of depth strata out to 90 m (295.3 ft) in northern California showed that harbor porpoise abundance declined significantly in waters deep than 60 m (196.9 ft) (Carettaet al., 2001b). Additionally, individuals of the Morro Bay stock appear to be concentrated at significantly higher densities in one specific area of their overall range, which NMFS is referring to as their “core range,” and density is much lower to both the North and South of this area. This core range has the larger number of harbor porpoise sightings and the largest number of harbor porpoise individuals observed during line-transect surveys and is defined for the purposes of this analysis from 34.755° through 35.425° North latitude (see transects 3 to 6 in Table 1 of Appendix B of the IHA application). For the Morro Bay stock, the best estimate of abundance is 2,044 animals and the minimum population estimate is 1,478 animals. There has been an increasing trend in harbor porpoise abundance in Morro Bay since 1988. The observed increase in abundance estimates for this stock since 1988 implies an annual growth rate of approximately 13%. Appendix B of the IHA application includes more detailed information on the density figures and calculations for the Morro Bay stock of harbor porpoise. Figure 1 of Appendix B shows the fine-scale density (including core habitat of higher density) as well as the proposed tracklines of Survey Box 4 and Survey Box 2.

    Refer to sections 3 and 4 of L-DEO and PG&E's application for detailed information regarding the abundance and distribution, population status, and life history and behavior of these other marine mammal species and their occurrence in the proposed project area. The application also presents how L-DEO and PG&E calculated the estimated densities for the marine mammals in the proposed survey area. NMFS has reviewed these data and determined them to be the best available scientific information for the purposes of the proposed IHA.

    Potential Effects on Marine Mammals

    Acoustic stimuli generated by the operation of the airguns, which introduce sound into the marine environment, may have the potential to cause Level B harassment of marine mammals in the proposed survey area. The effects of sounds from airgun operations might include one or more of the following: tolerance, masking of natura