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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices
TABLE 11DISTANCES TO LEVEL A CUMULATIVE SOUND EXPOSURE LEVEL SELcum HARASSMENT ACOUSTIC THRESHOLDS AND LEVEL B ROOT-MEAN-SQUARE SOUND PRESSURE LEVEL SPLrms ACOUSTIC THRESHOLD DUE TO 18
HOURS OF VIBRATORY PILE DRIVING
Marine mammal hearing group
Level A threshold SELcum dB re 1 Pa2 s
Maximum distance m to Level A
threshold
Level B threshold SPLrms dB re 1 Pa
Maximum distance m to Level B
threshold
199
198
173
201

1,470
0 63
103

120
120
120
120

36,766
36,766
36,766
36,766

Low-frequency cetaceans
Mid-frequency cetaceans
High-frequency cetaceans
Phocid pinnipeds

dB re 1 Pa = decibel referenced to 1 micropascal; Pa2 s = decibel referenced to 1 micropascal squared second.

HRG Surveys Isopleth distances to Level A
harassment thresholds for all types of HRG equipment and all marine mammal functional hearing groups were modeled using the NMFS User Spreadsheet and NMFS Technical Guidance 2018, which provides a conservative approach to exposure estimation.
NMFS has developed a user-friendly methodology for determining the rms sound pressure level SPLrms at the 160dB isopleth for the purposes of estimating the extent of Level B
harassment isopleths associated with HRG survey equipment NMFS, 2020.
This methodology incorporates frequency-dependent absorption and some directionality to refine estimated ensonified zones. South Fork Wind used NMFSs methodology with additional modifications to incorporate a seawater absorption formula and account for energy emitted outside of the primary beam of the source. For sources that
operate with different beam widths, the maximum beam width was used see Table 2. The lowest frequency of the source was used when calculating the absorption coefficient Table 2.
NMFS considers the data provided by Crocker and Fratantonio 2016 to represent the best available information on source levels associated with HRG
equipment and, therefore, recommends that source levels provided by Crocker and Fratantonio 2016 be incorporated in the method described above to estimate isopleth distances to the Level A harassment and Level B harassment thresholds. In cases when the source level for a specific type of HRG
equipment is not provided in Crocker and Fratantonio 2016, NMFS
recommends that either the source levels provided by the manufacturer be used, or, in instances where source levels provided by the manufacturer are unavailable or unreliable, a proxy from Crocker and Fratantonio 2016 be used
instead. Table 2 shows the HRG
equipment types that may be used during the proposed surveys and the sound levels associated with those HRG
equipment types.
Results of modeling using the methodology described above indicated that, of the HRG survey equipment planned for use by South Fork Wind that has the potential to result in Level B harassment of marine mammals, sound produced by the Applied Acoustics Dura-Spark UHD sparkers and GeoMarine Geo-Source sparker would propagate furthest to the Level B
harassment threshold 141 m; Table 12.
For the purposes of the exposure analysis, it was conservatively assumed that sparkers would be the dominant acoustic source for all survey days.
Thus, the distances to the isopleths corresponding to the threshold for Level B harassment for sparkers 141 m was used as the basis of the take calculation for all marine mammals.

TABLE 12DISTANCE TO WEIGHTED LEVEL A HARASSMENT AND LEVEL B HARASSMENT THRESHOLDS FOR EACH HRG
SOUND SOURCE OR COMPARABLE SOUND SOURCE CATEGORY FOR MARINE MAMMAL HEARING GROUPS
Distance to Level A threshold m Source
MF
SELcum threshold
LF
SELcum threshold
Distance to Level B m
HF
SPL0-pk threshold
HF
SELcum threshold
All species 160 dB
SPLrms threshold
PW
SELcum threshold
Shallow SBPs ET 216 CHIRP
ET 424 CHIRP
ET 512i CHIRP
GeoPulse 5430
TB CHIRP III

<1
0 0 <1
1.5

<1
0 0 <1 <1

2.9
0 <1
36.5
16.9

0
0 0 <1 <1

12
4 6
29
54

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Medium SBPs AA Triple plate S-Boom 700/1,000 J
AA, Dura-spark UHD 500 J/400 tip
AA, Dura-spark UHD 400+400
GeoMarine, Geo-Source dual 400 tip sparker

<1 <1 <1

0
0 0

0
0 0

4.7
2.8
2.8

<1 <1 <1

76
141
141

<1

0

0

2.8

<1

141

= not applicable; Pa = micropascal; AA = Applied Acoustics; CHIRP = Compressed High-Intensity Radiated Pulse; dB = decibels; ET =
EdgeTech; HF = high-frequency; J = joules; LF= low-frequency; MF = mid-frequency; PW = Phocids in water; re= referenced to; SBP = sub-bottom profiler; SELcum = cumulative sound exposure level in dB re 1 Pa2 s; SPL0-pk = zero to peak sound pressure level in dB re 1 Pa; TB =
teledyne benthos; UHD = ultra-high definition; USBL = ultra-short baseline.

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