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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices
TABLE 24PROPOSED CLEARANCE AND EXCLUSION ZONES 1 DURING SOUTH FORK WIND IMPACT PILE DRIVING WITH A
NOISE MITIGATION SYSTEMContinued Level A
harassment zone m SEL

Species
Harbor porpoise
Phocid Pinnipeds in Water:
Gray seal
Harbor seal

Level A
harassment zone m PK

Level B
harassment zone m
Pre-start clearance zone m
Exclusion zone m
Vessel separation distance m
365

301

4,684

450

450

50

120
85

10
10

4,684
4,684

150
150

150
150

50
50

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dB = decibel; SEL = cumulative sound exposure level PK = peak sound pressure level.
1 Zones are based upon the following modeling assumptions: 11-m monopile installation with inclusion of a difficult to install pile that requires approximately 8,000 hammer strikes and mitigated with10 dB broadband noise attenuation from a noise mitigation system. Only 1 pile out of the 16 total monopiles is expected to be a difficult pile.
2 No Level A exposures were calculated for blue whales resulting in no expected Level A exposure range; therefore, the exposure range for fin whales was used as a proxy due to similarities in species.

If a marine mammal is observed approaching or entering the relevant clearance zones prior to the start of pile driving, pile driving activity will be delayed until either the marine mammal has voluntarily left the respective clearance zone and been visually confirmed beyond that clearance zone, or, 30 minutes have elapsed without redetection of the animal in the case of mysticetes, sperm whales, Rissos dolphins and pilot whales, or 15
minutes have elapsed without redetection of the animal in the case of all other marine mammals.
Prior to the start of pile driving activity, the clearance zones will be monitored for 60 minutes using a combined effort of passive acoustic monitoring and visual observation to ensure that they are clear of the relevant species of marine mammals. Pile driving would only commence once PSOs have declared the respective clearance zones clear of marine mammals. Marine mammals observed within a clearance zone will be allowed to remain in the clearance zone i.e., must leave of their own volition, and their behavior will be monitored and documented. The clearance zones may only be declared clear, and pile driving started, when the entire clearance zones are visible i.e., when not obscured by dark, rain, fog, etc. for a full 60 minutes immediately prior to commencing pile driving. For North Atlantic right whales, the clearance zone may be declared clear if no visual or acoustic detections have occurred during the 60 minute monitoring period. If a species for which authorization has not been granted, or, a species for which authorization has been granted but the authorized number of takes have been met, approaches or is observed within the exclusion zone, shutdown would be required.

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Soft Start of Impact Pile Driving The use of a soft start procedure is believed to provide additional protection to marine mammals by warning marine mammals or providing them with a chance to leave the area prior to the hammer operating at full capacity, and typically involves a requirement to initiate sound from the hammer at reduced energy followed by a waiting period. South Fork Wind will utilize soft start techniques for impact pile driving including by performing 4
6 strikes per minute at 10 to 20 percent of the maximum hammer energy, for a minimum of 20 minutes. NMFS notes that it is difficult to specify the reduction in energy for any given hammer because of variation across drivers and, for impact hammers, the actual number of strikes at reduced energy will vary because operating the hammer at less than full power results in bouncing of the hammer as it strikes the pile, resulting in multiple strikes; however, as mentioned previously, South Fork Wind has proposed that they will target less than 20 percent of total hammer energy for the initial hammer strikes during soft start. Soft start would be required at the beginning of each days impact pile driving work and at any time following a cessation of impact pile driving of thirty minutes or longer.
Shutdown of Impact Pile Driving Equipment The purpose of a shutdown is to prevent some undesirable outcome, such as auditory injury or severe behavioral disturbance of sensitive species, by halting the activity. If a marine mammal is observed entering or within the respective exclusion zone Table 24 after pile driving has begun, the PSO will request a temporary cessation of pile driving.
In situations when shutdown is called for but South Fork Wind determines
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shutdown is not practicable due to imminent risk of injury or loss of life to an individual, or risk of damage to a vessel that created risk of injury or loss of life for individuals, reduced hammer energy would be implemented when practicable. After shutdown, pile driving may be initiated once all clearance zones are clear of marine mammals for the minimum speciesspecific time periods, or, if required to maintain installation feasibility.
Installation feasibility refers to ensuring that the pile installation results in a usable foundation for the WTG e.g., installed to the target penetration depth without refusal and with a horizontal foundation/tower interface flange.
Visibility Requirements Pile driving would not be initiated at night, or, when the full extent of all relevant clearance zones cannot be confirmed to be clear of marine mammals, as determined by the lead PSO on duty. The clearance zones may only be declared clear, and pile driving started, when the full extent of all clearance zones are visible i.e., when not obscured by dark, rain, fog, etc. for a full 60 minutes prior to pile driving.
Pile driving may continue after dark only when the driving of the same pile began no less than 90 minutes prior to civil sunset, when clearance zones were fully visible, and must proceed for human safety or installation feasibility reasons. PSOs would utilize night vision devices NVDs Infrared IR and/or thermal cameras to monitor clearance zones if pile driving continues past civil sunset.
Sound Attenuation Devices South Fork Wind would implement sound attenuation technology designed to result in an average of 10 dB
attenuation of impact pile driving noise see Acoustic Monitoring for Sound Source and Harassment Isopleth
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