NMFS Biological Opinion on U.S. Navy training ... - Govsupport.us

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FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013 mitigation zone, SURTASS LFA sonar transmissions is immediately suspended. Transmissions do not resume less than 15 minutes after: • All marine mammals have left the area of the LFA mitigation and buffer zones; and • There is no further detection of any marine mammal within the LFA mitigation and buffer zones as determined by the visual and/or passive or active acoustic monitoring. PASSIVE ACOUSTIC MONITORING. The U.S. Navy also uses passive acoustic monitoring for low frequency sounds generated by marine mammals when SURTASS is deployed. The following actions are associated with this monitoring: • If sounds are detected and estimated to be from a marine mammal, the technician will notify the Officer in Charge who will alert the HF/M3 sonar operator and visual observers; • If a sound produced by a marine mammal is detected, the technician will attempt to locate the sound source using localization software; and • If it is determined that the animal will pass within the LFA mitigation zone or 1-km buffer zone (prior to or during transmissions), then the Officer in Charge will order the delay/suspension of transmissions when the animal is predicted to enter either of these zones. HIGH FREQUENCY ACTIVE ACOUSTIC MONITORING. The Navy also conducts high frequency active acoustic monitoring (by using an enhanced, commercial-type high frequency sonar) to detect, locate, and track marine mammals (and possibly sea turtles) that could pass close enough to the SURTASS LFA sonar transmit array to exceed the 180-dB mitigation criterion. This Navy-developed HF/M3 sonar operates with a similar power level, signal type, and frequency as high frequency “fish finder” type sonars used worldwide by both commercial and recreational fishermen. The U.S. Navy ramps up the HF/M3 source slowly to operating levels over a period of no less than 5 minutes: The HF/M3 source will not increase its sound pressure level once a marine mammal is detected; ramp-up may proceed once marine mammals are no longer detected. HF/M3 sonar, LFA mitigation zone, and sound propagation. The extent of the LFA mitigation zone (i.e., within the 180-dB sound field) is estimated by onboard acoustic modeling and environmental data collected in situ. Factored into this calculation are SURTASS LFA sonar source physical parameters of tow speed, depth, vertical steering, signal waveform/wavetrain selection, and peak transmit source level. The HF/M3 sonar is located near the top of the SURTASS LFA sonar vertical line array. The HF/M3 sonar computer terminal for data acquisition/processing/display will be located in the SURTASS Operations Center. The HF/M3 sonar uses frequencies from 30 to 40 kHz with a variable bandwidth (1.5 to 6 kHz nominal); a 3-4 percent (nominal) duty cycle; a source level of 220 dB re 1 μPa (1 micropascal) at 1 m; a five-minute ramp-up period; and a maximum, nominal detection range of 2-2.5 km (1.08-1.35 nm). The HF/M3 sonar operates continuously while the SURTASS LFA sonar is deployed. When a marine animal is detected by the HF/M3 sonar, it automatically triggers an alert to the Watch Supervisor, who notifies the Officer in Charge. 146

FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013 The Officer in Charge then orders the immediate delay/suspension of SURTASS LFA sonar transmissions until the animal is determined to have moved beyond the mitigation zone. All contacts are recorded and provided to ong>NMFSong> as part of the long-term monitoring program associated with the proposed action. Analysis and testing of the HF/M3 sonar operating capabilities indicate that this system substantially increases the probability of detecting marine mammals within the LFA mitigation zone. It also provides an excellent monitoring capability (particularly for medium to large marine mammals) beyond the LFA mitigation zone, out to 2 to 2.5 km (1.08 to 1.35 nm). Recent testing of the HF/M3 sonar has demonstrated a probability of single-ping detection above 95 percent within the LFA mitigation zone for most marine mammals. EXPOSURE TO LOW-FREQUENCY ACTIVE SONAR. The dominant propagation paths for SURTASS LFA signals in low and middle latitudes would consist of convergence zone and bottom interaction (

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