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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices
1 The maximum density available for any month was used for each species to estimate the maximum potential exposures i.e., exposure estimates for all species are not for the same.
2 Subset of fin whale behaviors used to approximate model parameters.
3 Fin whale used as proxy species for exposure modeling.
4 Subset of sperm whale and Atlantic spotted dolphin behaviors used to approximate model parameters.
5 Subset of sperm whale behaviors used to approximate model parameters.
6 Harbor seal used as proxy species for exposure modeling.

Although exposures are presented according to a range of attenuation levels, proposed take numbers are based on an assumption of 10 dB attenuation and are shown below in Table 18. South Fork Wind considers an attenuation level of 10 dB achievable using a single big bubble curtain BBC, which is the most likely noise mitigation system that will be used during construction of SFWF. Recently reported in situ measurements during installation of large monopiles 8 m for more than 150 WTGs in comparable water depths >25 m and conditions in Europe indicate that attenuation levels of 10 dB
are readily achieved Bellmann, 2019;
Bellmann et al., 2020 using single BBCs
as a noise mitigation system. Designed to gather additional data regarding the efficacy of BBCs, the Coastal Virginia Offshore Wind CVOW pilot project systematically measured noise resulting from the impact driven installation of two 7.8 m monopiles, one with a noise mitigation system double bubble curtain dBBC and one without CVOW, unpublished data. Although many factors contributed to variability in received levels throughout the installation of the piles e.g., hammer energy, technical challenges during operation of the dBBC, reduction in broadband SEL using the dBBC
comparing measurements derived from the mitigated and the unmitigated
monopiles ranged from approximately 9 to 15 dB. The effectiveness of the dBBC as a noise mitigation measure was found to be frequency dependent, reaching a maximum around 1 kHz; this finding is consistent with other studies e.g., Bellman, 2014; Bellman et al., 2020. The noise measurements were incorporated into a dampened cylindrical transmission loss model to estimate distances to Level A and Level B harassment thresholds. The distances to Level A harassment and Level B
harassment thresholds estimated for the monopile with the dBBC were more than 90 percent and 74 percent smaller than those estimated for the unmitigated pile, respectively CVOW.

TABLE 18PROPOSED LEVEL A HARASSMENT AND LEVEL B HARASSMENT TAKES OF MARINE MAMMALS RESULTING
FROM IMPACT PILE DRIVING OF UP TO 15, 11-m MONOPILES WITHIN INCLUSION OF A SINGLE DIFFICULT PILE AT
SOUTH FORK WIND FARM USING 10 dB BROADBAND NOISE ATTENUATION
Abundance estimate
Species/stock Fin whale
Minke whale
Sei whale
Humpback whale
North Atlantic right whale
Blue whale
Sperm whale
Long-finned pilot whale
Atlantic spotted dolphin
Atlantic white-sided dolphin
Common dolphin
Rissos dolphin
Common bottlenose dolphin
Harbor porpoise
Gray seal
Harbor seal

6,802
21,968
6,292
1,393
412
402
4,349
39,921
39,921
93,233
172,974
35,493
62,851
95,543
505,000
75,834

Proposed takes 1
Level A
1 1
10
4 0
0 0
0 0
0 0
0 0
0 0
0

Level B
6 10
1 8
4 10
30
2 2
107
197
301
43
78
60
54

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1 Parentheses denote animal exposure model estimates. For species with no modeled exposures for Level A harassment or Level B harassment, proposed takes for impact pile driving are based on mean group sizes e.g., sei whale, blue whale, long-finned pilot whale: Kenney and Vigness-Raposa, 2010; sperm whale, Rissos dolphin: Barkaszi and Kelly, 2018.

South Fork Wind conservatively based their exposure modeling on the maximum piling scenario, including one difficult-to-drive monopile out of 16 and a compressed buildout schedule 16 piles installed over 20 days.
In addition, the acoustic modeling scenario represents only that which produced the largest harassment zones and does not reflect all the mitigation measures that will be employed during piling operations that will serve to reduce the Zone of Influence ZOI or increase mitigation actions, which may reduce take see the Proposed Mitigation
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section for details on the measures proposed for implementation.
Variability in monthly species densities is not considered in South Fork Winds take estimates for monopile driving, which are based on the highest mean density value for any month for each species. Given that less than 30
days of pile driving will occur, it is unlikely that maximum monthly densities would be encountered for all species.
Finally, start delays and shutdowns of pile hammering are not considered in the exposure modeling parameters for
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monopile driving. However, South Fork Wind will delay pile driving if a North Atlantic right whale is observed within the Level B harassment zone prior to initiating pile driving to avoid take and if a marine mammal is observed entering or within the respective exclusion zones after pile driving has commenced, an immediate shutdown of pile driving will be implemented unless South Fork Wind and/or its contractor determines shutdown is not practicable due to an imminent risk of injury or loss of life to an individual; or risk of damage to a vessel that creates risk of
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