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Federal Register / Vol. 86, No. 86 / Thursday, May 6, 2021 / Rules and Regulations
24347

TABLE 3THRESHOLDS 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.

Ensonified Area Here, we describe operational and environmental parameters of the activity that will feed into identifying the area ensonified above the acoustic thresholds, which include source levels.

The sound field in the project area is the existing background noise plus additional construction noise from the planned project. Marine mammals are expected to be affected via sound generated by the primary components of the project i.e., impact pile driving and vibratory pile driving. The largest
calculated Level B harassment zone extends 7.2 km 4.5 mi from the source though truncated by land in some directions, with an area of 4.7 km2 1.8
mi2, as calculated using geographic information system GIS data as determined by the transmission loss modeling.

TABLE 4PROJECT SOUND SOURCE LEVELS
Pile size and type
Installation method
24-in Square Concrete
16-in Composite

Impact
Impact
Vibratory
Vibratory

12-in Timber

RMS SPL
176
165
158
2 158

Peak SPL

SEL

Source
189
177

163
157

Illingworth and Rodkin, 2017.
Caltrans, 2015.1
Illingworth and Rodkin, 2017.
Illingworth and Rodkin, 2017.

1 These
source levels are from a 12-in timber pile Table 22, page 216.
typically recommends a proxy source level of 152dB RMS SPL for installation and removal of 12-in timber piles; however, the Navys application included specialized modeling described below using 158dB RMS SPL. Given that modeling and that 158dB RMS SPL is a more conservative source level, NMFS concurred with the use of 158dB RMS SPL as the proxy source level for 12-in timber piles.
2 NMFS

The Navy contracted the University of Washington, Applied Physics Laboratory APL to conduct sitespecific acoustic transmission loss
modeling for the project. The APLs full report is included in Appendix B of the Navys application. NMFS
independently reviewed and concurred
with the modeling in the report, and has adopted the resulting isopleths for the project, as included in Table 5.

TABLE 5LEVEL A AND LEVEL B HARASSMENT ISOPLETHS
Site
Level A harassment isopleth m
Pile size and type LF cetacean
I

MF cetacean
I

HF cetacean
I

Phocid
Level B
harassment isopleth m 1

Impact Pile Driving Pier 3
Pier 12
MWR Marina

khammond on DSKJM1Z7X2PROD with RULES

V-Area
Craney Island
Lamberts Point

16-in 16-in 24-in 16-in 24-in 16-in 16-in 16-in
Composite
Composite
Concrete
Composite
Concrete
Composite
Composite
Composite

18
18
52
11
42
11
16
19

<10m
27
24
59
18
47
17
21
28

Vibratory Pile Driving Pier 3
Pier 12
MWR Marina
V-Area

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16-in Composite/12-in Timber

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