Section 18.137 - Mitigation(a)Mitigation measures for all LOAs. The applicant, including all personnel operating under the applicant's authority (or "operators," including contractors, subcontractors, and representatives) must undertake the following activities to avoid and minimize take of sea otters by harassment.(1) Implement policies and procedures to avoid interactions with and minimize to the greatest extent practicable adverse impacts on sea otters, their habitat, and the availability of these marine mammals for subsistence uses.(2) Develop avoidance and minimization policies and procedures, in cooperation with the Service, that include temporal or spatial activity restrictions to be used in response to the presence of sea otters engaged in a biologically significant activity (e.g., resting, feeding, hauling out, mating, or nursing).(3) Cooperate with the Service's MMM Office and other designated Federal, State, and local agencies to monitor and mitigate the impacts of oil and gas industry activities on sea otters.(4) Allow Service personnel or the Service's designated representative to board project vessels or visit project work sites for the purpose of monitoring impacts to sea otters and subsistence uses of sea otters at any time throughout project activities so long as it is safe to do so.(5) Designate trained and qualified protected species observers (PSOs) to monitor for the presence of sea otters, initiate mitigation measures, and monitor, record, and report the effects of the activities on sea otters. The applicant is responsible for providing training to PSOs to carry out mitigation and monitoring.(6) Have an approved mitigation and monitoring plan on file with the Service MMM and onsite that includes the following information:(i) The type of activity and where and when the activity will occur (i.e., a summary of the plan of operation);(ii) Personnel training policies, procedures, and materials;(iii) Site-specific sea otter interaction risk evaluation and mitigation measures;(iv) Sea otter avoidance and encounter procedures; and(v) Sea otter observation and reporting procedures.(7) Contact affected subsistence communities and hunter organizations to identify any potential conflicts that may be caused by the proposed activities and provide the Service documentation of communications as described in § 18.134 .(b)Mitigation measures for in-water noise-generating work. The applicant must carry out the following measures:(1)Mitigation zones. Establish mitigation zones for project activities that generate underwater sound levels [GREATER THAN EQUAL TO]160 decibels (dB) between 125 hertz (Hz) and 38 kilohertz (kHz) (hereafter "noise-generating work"). (i) All dB levels are referenced to 1 [MICRO]Pa for underwater sound. All dB levels herein are dBRMS unless otherwise noted; dBRMS refers to the root-mean-squared dB level, the square root of the average of the squared sound pressure level, typically measured over 1 second.(ii) Mitigation zones must include all in-water areas where work-related sound received by sea otters will match the levels and frequencies in paragraph (b)(1) of this section. Mitigation zones will be designated as follows: (A) An Exclusion Zone (EZ) will be established throughout all areas where sea otters may be exposed to sound levels capable of causing Level A take as shown in the table in paragraph (b)(1)(iii) of this section.(B) The Safety Zone (SZ) is an area larger than the EZ and will include all areas within which sea otters may be exposed to noise levels that will likely result in Level B take as shown in the table in paragraph (b)(1)(iii) of this section.(C) Both the EZ and SZ will be centered on the sound source. The method of estimation and minimum radius of each zone will be specified in any LOA issued under § 18.135 and will be based on onsite sound source verification (SSV), if available, or the best available science.(D) Onsite SSV testing will be conducted prior to two-dimensional (2D) and three-dimensional (3D) seismic surveys.(E) Seismic surveys (2D and 3D) must be conducted using equipment that generates the lowest practicable levels of underwater sound within the range of frequencies audible to sea otters.(iii) Summary of acoustic exposure thresholds for take of sea otters from underwater sound in the frequency range 125 Hz-38 kHz: Table 1 to § 18.137(b)(1)(iii)
| Marine mammals | Injury (Level A) threshold1 | Disturbance (Level B) threshold |
| Impulsive | Non-impulsive | All |
| Sea otters | 232 dB peak; 203 dB SELCUM | 219 dB SELCUM | 160 dBRMS. |
1 Based on acoustic criteria for otariid pinnipeds from the National Marine Fisheries Service. Sound source types are separated into impulsive (e.g., seismic, pipe driving, sub-bottom profiler) and non-impulsive (drilling, water jet) and require estimation of the distance to the peak received sound pressure level (peak) and 24-hr cumulative sound exposure level (SELCUM).
(2)Monitoring. Designate trained and qualified PSOs or "observers" to monitor for the presence of sea otters in mitigation zones, initiate mitigation measures, and record and report the effects of project work on otters for all noise-generating work.(3)Mitigation measures for sea otters in mitigation zones. The following actions will be taken in response to otters in mitigation zones:(i) Sea otters that are under no visible distress within the SZ must be monitored continuously. Power down, shut down, or maneuver away from the sea otter if practicable to reduce sound received by the animal. Maintain 100-m (301-ft) separation distance whenever possible. Exposures in this zone are counted as one Level B take per animal per day.(ii) When sea otters are observed within or approaching the EZ, noise-generating work as defined in paragraph (b)(1) of this section must be immediately shut down or powered down to reduce the size of the zone sufficiently to exclude the animal from the zone. Vessel speed or course may be altered to achieve the same task. Exposures in this zone are counted as one Level A take per animal per day.(iii) When sea otters are observed in visible distress (for example, vocalizing, repeatedly spy-hopping, or fleeing), noise-generating work as defined in paragraph (b)(1) of this section must be immediately shut down or powered down to reduce the size of the zone sufficiently to exclude the animal from the zone.(iv) Following a shutdown, the noise-generating activity will not resume until the sea otter has cleared the EZ. The animal will be considered to have cleared the EZ if it is visually observed to have left the EZ or has not been seen within the EZ for 30 minutes or longer.(4)Ramp-up procedures. Prior to noise-generating work, a "ramp-up" procedure must be used to increase the levels of underwater sound from noise-generating work at a gradual rate. (i)Seismic surveys: A ramp-up will be used at the initial start of airgun operations and prior to restarting after any period greater than 10 minutes without airgun operations, including a power-down or shutdown event (described in paragraphs (b)(6) and (7) of this section). During geophysical work, the number and total volume of airguns will be increased incrementally until the full volume is achieved. The rate of ramp-up will be no more than 6 dB per 5-minute period. Ramp-up will begin with the smallest gun in the array that is being used for all airgun array configurations. During the ramp-up, the applicable mitigation zones (based on type of airgun and sound levels produced) must be maintained. It will not be permissible to ramp up the full array from a complete shutdown in thick fog or at other times when the outer part of the EZ is not visible. Ramp-up of the airguns will not be initiated if a sea otter is sighted within the EZ at any time.(ii)Pile/pipe driving: A ramp-up of the hammering will precede each day's pipe/pile driving activities or if pipe/pile driving has ceased for more than 1 hour. The EZ will be determined clear of sea otters 30 minutes prior to a ramp-up to ensure no sea otters are within or entering the EZ. Initial hammering starts will not begin during periods of poor visibility (e.g., night, fog, wind) when the entire EZ is not visible. The ramp-up procedure for impact hammers involves initially starting with three soft strikes at 40 percent energy, followed by a 1-minute waiting period followed by two subsequent three-strike sets. For vibratory hammers, initial noise generation will be limited to 15 seconds at a reduced energy level, followed by a 1-minute waiting period. This cycle will be repeated two additional times. Monitoring will occur during all hammering sessions.(iii)All activities: Any shutdown due to sea otters sighted within the EZ must be followed by a 30-minute all-clear period and then a standard full ramp-up. Any shutdown for other reasons resulting in the cessation of the sound source for a period greater than 30 minutes must also be followed by full ramp-up procedures. If otters are observed during a ramp-up effort or prior to startup, a PSO must record the observation and monitor the animal's position until it moves out of visual range. Noise-generating work may commence if, after a full and gradual effort to ramp up the underwater sound level, the otter is outside of the EZ and does not show signs of visible distress (for example, vocalizing, repeatedly spy-hopping, or fleeing).(5)Startup procedures.(i) Visual monitoring must begin at least 30 minutes prior to, and continue throughout, ramp-up efforts.(ii) Visual monitoring must continue during all noise-generating work occurring in daylight hours.(6)Power-down procedures. A power-down procedure involves reducing the volume of underwater sound generated to prevent an otter from entering the EZ.(i) Whenever a sea otter is detected outside the EZ and, based on its position and motion relative to the noise-generating work, appears likely to enter the EZ but has not yet done so, operators may reduce power to noise-generating equipment as an alternative to a shutdown.(ii) Whenever a sea otter is detected in the SZ, an operator may power down when practicable to reduce Level B take.(iii) During a power-down of seismic work, the number of airguns in use may be reduced, such that the EZ is reduced, making the sea otters unlikely to enter the EZ. A mitigation airgun (airgun of small volume such as the 10-in3 gun) will be operated continuously during a power-down of seismic work.(iv) After a power-down, noise-generating work will not resume until the sea otter has cleared the applicable EZ. The animal will be considered to have cleared the applicable zone if it is visually observed to have left the EZ and has not been seen within the zone for 30 minutes.(7)Shutdown procedure. A shutdown occurs when all noise-generating work is suspended.(i) Noise-generating work will be shut down completely if a sea otter enters the EZ.(ii) The shutdown procedure will be accomplished within several seconds of the determination that a sea otter is either in or about to enter the EZ or as soon as practicable considering worker safety and equipment integrity.(iii) Noise-generating work will not proceed until all sea otters have cleared the EZ and the PSOs on duty are confident that no sea otters remain within the EZ. An otter will be considered to have cleared the EZ if it is visually observed to have left the EZ or has not been seen within the zone for 30 minutes.(iv) Visual monitoring must continue for 30 minutes after use of the acoustic source ceases or the sun sets, whichever is later.(8)Emergency shutdown. If observations are made or credible reports are received that one or more sea otters are within the area of noise-generating work and are indicating acute distress associated with the work, such as any injury due to seismic noise or persistent vocalizations indicating separation of mother from pup, the work will be immediately shut down and the Service contacted. Work will not be restarted until review and approval by the Service.(9) To ensure the proposed activities remain consistent with the estimated take of sea otters, operators may not conduct 3D seismic surveys where doing so will generate underwater noise levels that are likely to exceed acoustic exposure thresholds within areas of estimated sea otter densities greater than 0.026 otters per km. Maps of the areas will be provided to 3D seismic operators and may be adjusted based on SSV results. This does not apply to 2D seismic surveys.(c)Mitigation for all in-water construction and demolition activity.(1) The applicant must implement a minimum EZ of a 10-m radius around the in-water construction and demolition. If a sea otter comes within or approaches the EZ, such operations must cease. A larger EZ may be required for some activities, such as blasting, and will be specified in the LOA.(2) All work in intertidal areas shall be conducted during low tide when the site is dewatered to the maximum extent practicable.(3) The applicant must evaluate alternatives to pile-supported facilities. If no practicable alternative exists, the applicant must then evaluate the use of sound-attenuation devices such as pile caps and cushions, bubble curtains, and dewatered cofferdams during construction. The Service may require sound-attenuation devices or alternatives to pile-supported designs.(d)Measures for vessel-based activities.(1) Vessel operators must take every precaution to avoid harassment of sea otters when a vessel is operating near these animals.(2) Vessels must remain at least 500 m from rafts of otters unless safety is a factor.(3) Vessels must reduce speed and maintain a distance of 100 m (328 ft) from all sea otters unless safety is a factor.(4) Vessels must not be operated in such a way as to separate members of a group of sea otters from other members of the group.(5) When weather conditions require, such as when visibility drops, vessels must adjust speed accordingly to avoid the likelihood of injury to sea otters.(6) Vessels in transit and support vessels must use established navigation channels or commonly recognized vessel traffic corridors, and must avoid alongshore travel in shallow water ([LESS THAN]20 m) whenever practicable.(7) All vessels must avoid areas of active or anticipated subsistence hunting for sea otters as determined through community consultations.(8) Vessel operators must be provided written guidance for avoiding collisions and minimizing disturbances to sea otters. Guidance will include measures identified in paragraphs (d)(1) through (7) of this section.(e)Mitigation measures for aircraft activities.(1) Aircraft must maintain a minimum altitude of 305 m (1,000 ft) to avoid unnecessary harassment of sea otters, except during takeoff and landing, and when a lower flight altitude is necessary for safety due to weather or restricted visibility.(2) Aircraft must not be operated in such a way as to separate members of a group of sea otters from other members of the group.(3) All aircraft must avoid areas of active or anticipated subsistence hunting for sea otters as determined through community consultations.(4) Unmanned aerial systems or drones must not cause take by harassment of sea otters. Measures for avoidance of take may be required in an LOA, and may include maintaining a minimum altitude and horizontal distance no less than 100 m away from otters, conducting continuous visual monitoring by PSOs, and ceasing activities in response to sea otter behaviors indicating any reaction to drones.