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Federal Register / Vol. 86, No. 23 / Friday, February 5, 2021 / Notices TABLE 5THRESHOLDS IDENTIFYING THE ONSET OF PERMANENT THRESHOLD SHIFT
PTS onset acoustic thresholds
received level Hearing group
Impulsive
Low-Frequency LF Cetaceans
Mid-Frequency MF Cetaceans
High-Frequency HF Cetaceans
Phocid Pinnipeds PW Underwater
Otariid Pinnipeds OW Underwater

Cell Cell Cell Cell Cell
1:
3:
5:
7:
9:

Lpk,flat:
Lpk,flat:
Lpk,flat:
Lpk,flat:
Lpk,flat:

219
230
202
218
232

dB;
dB;
dB;
dB;
dB;

Non-impulsive
LE,LF,24h: 183 dB
LE,MF,24h: 185 dB
LE,HF,24h: 155 dB
LE,PW,24h: 185 dB
LE,OW,24h: 203 dB

Cell Cell Cell Cell Cell
2: LE,LF,24h: 199 dB.
4: LE,MF,24h: 198 dB.
6: LE,HF,24h: 173 dB.
8: LE,PW,24h: 201 dB.
10 : LE,OW,24h: 219 dB.

Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should also be considered.
Note: Peak sound pressure Lpk has a reference value of 1 Pa, and cumulative sound exposure level LE has a reference value of 1Pa2s.
In this Table, thresholds are abbreviated to reflect American National Standards Institute standards ANSI 2013. However, peak sound pressure is defined by ANSI as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript flat is being included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function LF, MF, and HF
cetaceans, and PW and OW pinnipeds and that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could be exceeded in a multitude of ways i.e., varying exposure levels and durations, duty cycle. When possible, it is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be exceeded.

Acoustic Modeling Here, NMFS describes operational and environmental parameters of the activity that will feed into identifying the area ensonified above the acoustic thresholds, which include source levels and transmission loss coefficient.
Impact Pile Driving: Acoustic Range As described above, South Fork Wind is proposing to install up to 15 WTGs and one OSS in the SFWF i.e., a maximum of 16 foundations. Two piling scenarios may be encountered in the construction of the project and were therefore considered in the acoustic
modeling study conducted to estimate the potential number of marine mammal exposures above relevant harassment thresholds: 1 Maximum design, including one difficult to drive pile, and 2 standard design with no difficult to drive pile included.
In recognition of the need to ensure that the range of potential impacts to marine mammals from the various potential scenarios are accounted for, piling scenarios were modeled separately in order to conservatively assess the impacts of each. The two monopile installation scenarios modeled are:

1 The maximum design consisting of fifteen piles requiring 4,500 strikes per pile per 24 hrs, and one difficult to drive pile requiring 8,000 strikes per 24 hrs.
2 The standard design consisting of sixteen piles requiring 4,500 strike per pile per 24 hrs.
Representative hammering schedules of increasing hammer energy with increasing penetration depth were modeled, resulting in, generally, higher intensity sound fields as the hammer energy and penetration increases Table 6.

TABLE 6HAMMER ENERGY SCHEDULE FOR MONOPILE INSTALLATION
Standard pile strike count 4,500 total
Energy level kilojoulekJ

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1,000
1,500
2,500
4,000

Monopiles were assumed to be vertical and driven to a penetration depth of 45 m. While pile penetrations across the site would vary, this value was chosen as a reasonable penetration depth. All acoustic modeling was performed assuming that only one pile is driven at a time.
Additional modeling assumptions for the monopiles were as follows:
One pile installed per day.
10.97 m steel cylindrical piling with wall thickness of 10 cm.
Impact pile driver: IHC S4000
4000 kilojoules kJ rated energy; 1977
kilonewtons kN ram weight.
Helmet weight: 3234 kN.

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Sound fields produced during impact pile driving were modeled by first characterizing the sound signal produced during pile driving using the industry-standard GRLWEAP wave equation analysis of pile driving model and JASCO Applied Sciences JASCO
Pile Driving Source Model PDSM. The full JASCO modeling report can be found at https
www.fisheries.noaa.gov/permit/
incidental-take-authorizations-undermarine-mammal-protection-act and we provide a summary of the modelling effort below.
Underwater sound propagation i.e., transmission loss as a function of range
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500
1,000
1,500
1,500

Difficult pile strike count 8,000 total 800
1,200
3,000
3,000

Pile penetration m 06
623.5
23.541
4145

from each source was modeled using JASCOs Marine Operations Noise Model MONM for multiple propagation radials centered at the source to yield 3D transmission loss fields in the surrounding area. The MONM computes received per-pulse SEL for directional sources at specified depths. MONM uses two separate models to estimate transmission loss.
At frequencies less than 2 kHz, MONM computes acoustic propagation via a wide-angle parabolic equation PE
solution to the acoustic wave equation based on a version of the U.S. Naval Research Laboratorys Range-dependent Acoustic Model RAM modified to
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