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Federal Register / Vol. 86, No. 33 / Monday, February 22, 2021 / Notices
Mitigation for Marine Mammals and Their Habitat In addition to the measures described later in this section, AGDC will employ the following mitigation measures:
Conduct briefings between construction supervisors and crews and the marine mammal monitoring team prior to the start of all pile driving activity and when new personnel join the work, to explain responsibilities,
communication procedures, marine mammal monitoring protocol, and operational procedures;
For in-water construction, heavy machinery activities other than pile driving, if a marine mammal comes within 10 m 33 ft, operations shall cease and vessels shall reduce speed to the minimum level required to maintain steerage and safe working conditions;
For those marine mammals for which Level B harassment take has not
been requested, in-water pile installation/removal will shut down immediately when it is safe to do so if such species are observed within or entering the Level B harassment zone;
and If take reaches the authorized limit for an authorized species, pile installation will be stopped as these species approach the Level B
harassment zone to avoid additional take.

TABLE 17SHUTDOWN ZONES DURING PILE INSTALLATION AND REMOVAL
Activity
Shutdown Zone m
Hammer Type LF cetaceans
11.5-inch H-Pile
14-inch H-Pile

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48-inch Pipe Pile
Sheet Piles
Screeding

Aircraft must transit at an altitude of 457 m 1,500 ft or higher, to the extent practicable, while maintaining Federal Aviation Administration flight rules e.g., avoidance of cloud ceiling, etc., excluding takeoffs and landing. If flights must occur at altitudes less than 457 m 1,500 ft due to environmental conditions, aircraft must make course adjustments, as needed, to maintain at least a 457 m 1,500 ft separation from all observed marine mammals.
Helicopters if used must not hover or circle above marine mammals. A
minimum transit altitude is expected to reduce the potential for disturbance to marine mammals from transiting aircraft.
AGDC is required to implement all mitigation measures described in the biological opinion issued on June 3, 2020.
The following mitigation measures would apply to AGDCs in-water construction activities.
Establishment of Shutdown Zones AGDC will establish shutdown zones for all pile driving and removal activities.
The purpose of a shutdown zone is generally to define an area within which shutdown of the activity would occur upon sighting of a marine mammal or in anticipation of an animal entering the defined area. Shutdown zones will vary based on the activity type and marine mammal hearing group see Table 17.
The largest shutdown zones are generally for low frequency cetaceans as shown in Table 17. In this instance, the largest shutdown zone for low frequency cetaceans is 1,600 m. AGDC
expects that they will be able to
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Impact
Impact
Vibratory
Impact
Vibratory

effectively observe phocids at distances up to 500 m, large cetaceans at 24 km, and belugas at 23 km.
The placement of PSOs during all pile driving and removal activities described in detail in the Monitoring and Reporting section will ensure that the entire shutdown zone is visible during pile installation. If visibility degrades to where the PSO determines that they cannot effectively monitor the entire shutdown zone during pile driving, the applicant may continue to drive the pile section that was being driven to its target depth when visibility degraded to unobservable conditions, but will not drive additional sections of pile. Pile driving may continue during low light conditions to allow for the evaluation of NVDs and IR sensing devices.
Monitoring for Level A and Level B
HarassmentAGDC will monitor the Level B harassment zones areas where SPLs are equal to or exceed the 160 dB
rms threshold for impact driving and the 120 dB rms threshold during vibratory driving and Level A
harassment zones, to the extent practicable. Monitoring the Level A and Level B harassment zones enables observers to be aware of and communicate the presence of marine mammals in the project area outside the shutdown zone and thus prepare for a potential shutdown of activity should the animal enter the shutdown zone.
Placement of PSOs on elevated structures on West Dock will allow PSOs to observe phocids within the Level A and Level B harassment zones, to an estimated distance of 500 m.

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1,200
1,200
10
1,600
20
215

MF cetaceans
Phocids
50
50
10
50
10

500
500
10
500
10

However, due to the large Level A and Level B harassment zones Table 6, PSOs will not be able to effectively observe the entire zones during all activities for all species. Therefore, marine mammal exposures within the visible portion of the harassment zones will be recorded, and potential exposures within the entire harassment zones will be estimated based upon the number of observed exposures and the percentage of the Level A or Level B
harassment zone that was not visible.
AGDC will also conduct acoustic monitoring as described in the Monitoring and Reporting section, below.
Pre-activity MonitoringPrior to the start of daily in-water construction activity, or whenever a break in pile driving or removal of 30 minutes or longer occurs, PSOs will observe the shutdown zone and the visible portions of the Level A and Level B harassment zones for a period of 30 minutes. If a marine mammal is observed within the shutdown zone, a soft-start cannot proceed until the animal has left the zone or has not been observed for 15
minutes pinnipeds or 30 minutes cetaceans. When a marine mammal for which Level B harassment take is authorized is present in the Level B
harassment zone, activities may begin and Level B harassment take will be recorded. If the entire Level B
harassment zone is not visible at the start of construction pile driving or removal activities can begin. If work ceases for more than 30 minutes, the pre-activity monitoring of both the Level
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