Federal Register - February 22, 2021
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Source: Federal Register
10673
Federal Register / Vol. 86, No. 33 / Monday, February 22, 2021 / Notices Caltrans 2015 for 60-in CISS piles are attenuated source levels, not unattenuated source levels. Those piles were driven within either a cofferdam see section I.3.2 in Caltrans 2015 or a sound attenuation device isolation casing with a bubble curtain, see sections I.11 and I.11.2. NMFS
indicated in the Federal Register notice that AGDC would not be using a sound attenuation device 85 FR 43406; July 16, 2020. Therefore, NMFS use of the source levels from Caltrans was not appropriate. Caltrans 2015 did not include unattenuated source levels for impact installation of 60-in piles, and the attenuated source levels are less than unattenuated source levels for impact installation of 48-in piles.
For impact installation of 48-in piles, NMFS has consistently used and deemed as best available source levels from Austin et al. 2016; see 84 FR
31004; June 28, 2019, 85 FR 19312;
April 6, 2020, 85 FR 21404; April 17,
2020, 85 FR 31151; May 22, 2020, 85 FR
40252; July 6, 2020. The source levels of 186.7 decibels dB re 1 micro Pascal squared mPa2-sec single-strike s-s at 11 m, 198.6 dB re 1 mPa root-meansquare rms at 10 m, and 212.5 dB re 1 mPa peak pk at 11 m should have been used for AGDCs proposed activities as well see values for pile IP5
in Tables 9, 11, and 7, respectively, in Austin et al. 2016. Those source levels are unattenuated, originate from Alaska, and have been used consistently in other recent IHAs that involve impact installation of 48-in piles. As such, the Commission recommended that NMFS
use unattenuated source levels of 186.7
dB re 1 mPa2-secs-s at 11 m, 198.6 dB
re 1 mPa rms at 10 m, and 212.5 dB re 1 mPa peak at 11 m from Austin et al.
2016 for impact installation of 48-in piles rather than the attenuated source levels from Caltrans 2015.
Response: The Commission is correct that the proxy source levels NMFS used
for impact driving 48-in piles 60-in CISS piles are attenuated source levels, and that AGDC is not using a sound attenuation device. However, NMFS
disagrees that the Austin et al. 2016
source levels suggested by the commenter are more appropriate than the proxy used in the proposed IHA.
NMFS reviewed numerous source levels for impact installation of 48-in piles normalized to 10 m Table 1. The proxy source levels used for impact installation of 48-in piles in the proposed authorization pk, root mean square sound pressure level SPLrms and sound exposure level SEL are higher, and therefore more conservative, than the median source level in NMFS
review of available source levels for impact installation of 48-in piles. Given the shallow water depth at the Prudhoe Bay site, we expect that source levels for the AK LNG project will be lower than average. Note that AGDC will also conduct SSV to verify the zone sizes.
TABLE 1ACOUSTIC DATA FROM UNATTENUATED IMPACT INSTALLATION OF 48 STEEL PIPE PILES
tkelley on DSKBCP9HB2PROD with NOTICES2
Processed data of datasets used to calculate the median:
Source dist. m
Measured SPLpk dB re 1
Pa
Measured SPLrms dB re 1
Pa
Measured SEL
dB re 1
Pa2s
Normalized to 10-m SL
SPLpk dB re 1 Pa @10 m
Normalized to 10m SL
SPLrms dB re 1 Pa @10 m
Normalized to 10m SL
SEL
dB re 1
Pa2s @10
m
Location
TP11 2
10
207
192
179.5
207
192
179.5
Naval Base Kitsap.
TP5 2
10
207.5
192
180.5
207.5
192
180.5
Naval Base Kitsap.
A3 3
10
212.3
198.6
183.1
212.3
198.6
183.1
Columbia River Crossing.
A4 2
10
213.45
199.65
183.05
213.45
199.65
183.05
Columbia River Crossing.
B2 3
10
207.1
196.7
182
207.1
196.7
182
Columbia River Crossing.
10
200
183
173
200
183
173
Philadelphia Naval Shipyard.
10
200
185
174
200
185
174
Philadelphia Naval Shipyard.
10
203
187
176
203
187
176
Philadelphia Naval Shipyard.
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Report
Naval Base Kitsap at Bangor Test Pile Program Acoustic Monitoring Report I&R 2012; p. 61, 64, 67.
Naval Base Kitsap at Bangor Test Pile Program Acoustic Monitoring Report I&R 2012; p. 62, 64, 67.
Columbia River Crossing Test Pile Report David Evans & Associates, 2011; pdf:
97.
Columbia River Crossing Test Pile Report David Evans & Associates, 2011; pdf:
109.
Columbia River Crossing Test Pile Report David Evans & Associates, 2011; pdf:
130.
NAVFAC Pile-driving at Atlantic Fleet Naval Installations 2017; p. 31.
NAVFAC Pile-driving at Atlantic Fleet Naval Installations 2017; p. 31.
NAVFAC Pile-driving at Atlantic Fleet Naval Installations 2017; p. 31.
