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Federal Register / Vol. 86, No. 122 / Tuesday, June 29, 2021 / Notices
TABLE 7NMFS TECHNICAL GUIDANCE 2020 USER SPREADSHEET INPUT TO CALCULATE PTS ISOPLETHS FOR IMPACT
PILE DRIVINGContinued User spreadsheet inputimpact pile driving spreadsheet Tab E.1 impact pile driving used 24-in piles permanent Minutes per pile
Number of piles per day
Propagation xLogR
Distance of source level measurement meters

8-in pile DTH

8-in pile DTH

8-in pile DTH

24-in pile DTH

24-in pile DTH

24-in pile DTH

3 15

60
1 15

120
1 15

180
1 15

60
1 15

90
1 15

180
1 15

10

10

10

10

10

10

10

TABLE 8NMFS TECHNICAL GUIDANCE 2020 USER SPREADSHEET OUTPUTS TO CALCULATE LEVEL A HARASSMENT
PTS ISOPLETHS
User spreadsheet output
PTS isopleths meters Level A harassment Sound source level at 10 m
Activity
Low-frequency cetaceans
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Mid-frequency cetaceans
I

High-frequency cetaceans
I

Phocid
I

Otariid
Vibratory Pile Driving/Removal 16-in steel pile removal
24-in steel pile temporary installation and removal ..
24-in steel pile permanent

161 SPL
161 SPL
161 SPL

10.8
10.8
10.8

1.0
1.0
1.0

16.0
16.0
16.0

6.6
6.6
6.6

0.5
0.5
0.5

112.6
85.9
54.1

4.0
3.1
1.9

134.1
102.3
64.5

60.3
46.0
29.0

4.4
3.3
2.1

35.8
56.9
74.5
166.3
218.0
346.0

1.3
2.0
2.7
5.9
7.8
12.3

42.7
67.8
88.8
198.1
259.6
412.1

19.2
30.4
39.9
89.0
116.6
185.2

1.4
2.2
2.9
6.5
8.5
13.5

Impact Pile Driving 24-in steel permanent installation 3 piles a day
24-in steel permanent installation 2 piles a day
24-in steel permanent installation 1 piles a day

181 SEL/193 SPL
181 SEL/193 SPL
181 SEL/193 SPL
DTH

8-in steel 60 min
8-in steel 120 min
8-in steel 180 min
24-in steel 60 min
24-in steel 90 min
24-in steel 180 min

Level B Harassment Utilizing the practical spreading loss model, the AKDOT&PF determined underwater noise will fall below the behavioral effects threshold of 120 dB
rms for marine mammals at the distances shown in Table 9 for vibratory
144
144
144
154
154
154

SEL/166
SEL/166
SEL/166
SEL/166
SEL/166
SEL/166

SPL
SPL
SPL
SPL
SPL
SPL

I

pile driving/removal, and DTH. With these radial distances, the largest Level B harassment zone calculated was for DTH at 11,659 m. For calculating the Level B harassment zone for impact driving, the practical spreading loss model was used with a behavioral
I

I

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threshold of 160 dB rms. The maximum radial distance of the Level B
harassment zone for impact piling equaled 1,585 m for 24-in piles. Table 9 below provides all Level B harassment radial distances m during the AKDOT&PFs proposed activities.

TABLE 9RADIAL DISTANCES METERS TO RELEVANT BEHAVIORAL ISOPLETHS
Received level at 10 meters m
Activity
Level B harassment zone m

Vibratory Pile Driving/Removal and DTH
16-in steel piles
24-in steel piles
8-in and 24-in DTH

161 SPL
161 SPL
166 SPL

5,415 calculated 5,412.
5,415 calculated 5,412.
11,660 calculated 11,659.

Impact Pile Driving 24-in steel piles

181 SEL/193 SPL

1,585.

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Numbers rounded up to nearest 5 meters. These specific rounded distances are for monitoring purposes rather than take estimation.

Marine Mammal Occurrence and Take Calculation and Estimation In this section we provide the information about the presence, density, or group dynamics of marine mammals
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that will inform the take calculations.
Potential exposures to impact pile driving, vibratory pile driving/removal and DTH noises for each acoustic threshold were estimated using group size estimates and local observational
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data. As shown above, distances to Level A harassment thresholds for project activities are relatively small and mitigation i.e., shutdown zones is expected to avoid Level A harassment from these activities. Accordingly, take
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