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Federal Register / Vol. 86, No. 33 / Monday, February 22, 2021 / Notices
specified activity are found in the Federal Register notices for the initial IHA, including the proposed 2019 IHA
84 FR 13252; April 4, 2019 and final 2019 IHA 84 FR 24476; May 28, 2019.
Marine mammal occurrence data applicable to this authorization remain unchanged from the previously issued IHA. Similarly, the stocks taken, methods of estimating take, and types of take remain unchanged from the
previously issued IHA. As mentioned previously, due to the use of slightly different pile sizes, the source levels included in the renewal request Table 1 are nearly identical, rather than identical, to those analyzed in the 2019
IHA and included in the initial IHA. In addition, the number of construction days and piles proposed in the Renewal request Tables 2 and 3 are fewer than those included in the initial IHA.

Finally, the proposed maximum ensonified area, or region of influence ROI, is smaller 0.42 square kilometers km2 than that analyzed in the initial IHA 0.85 km2 because the completed construction e.g., southern closure wall and majority of the caisson seat foundation created additional barriers to sound produced by construction activities.

TABLE 1SUMMARY OF IN-WATER PILE DRIVING SOURCE LEVELS SL AT 10 m FROM SOURCE

30-inch 27-inch 27-inch 25-inch
steel pipe 1
sheet pile 2
sheet pile 3
sheet pile 2

SPLpk, dB re 1 Pa
Installation method
Pile type and size

Vibratory
Vibratory
Impact
Vibratory

SPLrms, dB re 1 Pa
SEL, dB
re 1 Pa2-s
167
167
196
163

167
167
181
163

NA
NA
211 205
NA

175
163
190
163

175
163
180
163

SPLpk, dB re 1 Pa = peak sound pressure level referenced to 1 micropascal; SPLrms = root mean square sound pressure level referenced to 1 micropascal; SEL = sound exposure level referenced to 1 micropascal-squared-second; values from 2019 IHA in parentheses: 1 vibratory installation of 36 in steel pile; 2 vibratory installation of 24 in sheet pile; 3 impact installation of 24 in sheet pile.

Table 2 includes information for both the subset of activities using vibratory pile driving the Navy will not complete before the current IHA expires e.g.,
completion of the caisson seat foundation and installation of the guide dolphins for the caisson seat float-in structure as well as the newly proposed
activity, construction of a temporary blast wall.

TABLE 2DISTANCES AND AREAS OF HARASSMENT ZONES, AND ASSOCIATED CONSTRUCTION ACTIVITIES FOR VIBRATORY
PILE DRIVING
Level A harassment injury PTS onset Section
Pile size inch in and count
Caisson seat foundation.
Guide dolphins for caisson float-in.
Temporary blast wall Temporary blast wall
27 in steel sheet 20

Total pile driving days
Behavior disturbance Level B harassment
High-frequency cetaceans 173 dB
SELcum1 threshold radial distance/area
Phocid pinnipeds 201 dB
SELcum threshold radial distance/area
All marine mammals 120
dB RMS threshold radial distance/ROI

2

25.4 m/0.001746 km2

10.4 m/0.000338 km2

13,594 m/0.42 km2.

30 in steel pipe 12

12

4.8 m/0.000072 km2

2.0 m/0.000012 km2

13,594 m/0.42 km2.

30 in steel pipe 15
25 in steel sheet 70

8
7

7.7 m/0.000185 km2
22.5 m/0.001378 km2

3.2 m/0.000032 km2
9.2 m/0.000264 km2

13,594 m/0.42 km2.
13,594 m/0.42 km2.

Region of influence ROI; potentially ensonified area capped due to landmass and existing Dry Dock 1 structural interception of noise.
1 SEL
cum = cumulative sound exposure level.

Table 3 provides information for impact driving of sheet piles required to
complete construction of the caisson seat foundation.

TABLE 3DISTANCES AND AREAS OF HARASSMENT ZONES, AND ASSOCIATED CONSTRUCTION ACTIVITIES FOR IMPACT
PILE DRIVING

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Level A harassment injury PTS onset Section
Pile size inchin and count
Total pile driving days
Caisson seat foundation.

27 in steel sheet 20

2

Behavior disturbance Level B

High-frequency cetaceans 155 dB
SELcum1 threshold
Phocid pinnipeds seals 185 dB SELcum threshold
All marine mammals 160
dB RMS threshold radial distance/ROI

2,055.5 m/0.42 km2

923.5 m/0.40 km2

2,512 m/0.42 km2.

Region of influence ROI; potentially ensonified area capped due to landmass and existing Dry Dock 1 structural interception of noise.
1SEL
cum = cumulative sound exposure level.

Takes estimated in the renewal request were zero for three of the five
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species included in the 2019 and initial IHAs harbor porpoise, hooded seal, and
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harp seal because the densities for these species were zero at the specified
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