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Federal Register / Vol. 86, No. 122 / Tuesday, June 29, 2021 / Notices measurements available for certain pile types and sizes from the similar environments recorded from underwater pile driving projects in Alaska that were
evaluated and used as proxy sound source levels to determine reasonable sound source levels likely result from the AKDOT&PFs pile driving and
removal activities Table 5. Many source levels used were more conservative as the values were from larger pile sizes.

TABLE 5PROPOSED SOUND SOURCE LEVELS
Method and pile type
SSL at 10 meters
Literature Source
Continuous Vibratory Pile Driving and DTH
16-in Steel Piles
24-in Steel Piles
24-in DTH b
8-in DTH c

dB rms 161
161
166
166

Navy 2012, 2015
Navy 2012, 2015
Denes et al. 2016 Table 72 b
NMFS c
Impulsive Impact Pile Driving and DTH

dB rms
dB SEL

24-in Steel Piles
24-in DTH b
8-in DTH c

193

181
154
144

dB Peak
Federal Register sources a A, B, C, H.
C, D, E, H, I.
B, C, F, G.

210
170

Navy 2015
Denes et al. 2016 b
Reyff 2020.

D, H, I.

a Federal Register FR sources:
A: 84 FR 24490, City of Juneau Waterfront Improvement Project, Juneau, Alaska.
B: 85 FR 4278, Statter Harbor Improvement Project, Auke Bay, Alaska.
C: 85 FR 673, Tongass Narrows Ferry Berth Improvements, Ketchikan, Alaska.
D: 85 FR 19294, Port of Alaskas Petroleum and Cement Terminal, Anchorage, Alaska.
E: 84 FR 56767, Auke Bay Ferry Terminal Modifications and Improvements Project, Juneau, Alaska.
F: 85 FR 18196, Gastineau Channel Historical Society Sentinel Island Moorage Float Project, Juneau, Alaska.
G: 85 FR 12523, Ward Cove Cruise Ship Dock Project, Juneau, Alaska.
H: 83 FR 29749, City Dock and Ferry Terminal, Tenakee Springs, Alaska.
I: 82 FR 48987, Sand Point City Dock Replacement Project, Sand Point, Alaska.
b DTH pile installation is treated as a continuous sound for Level B calculations and impulsive for Level A calculations.
c Tension anchor installation 8-in DTH is currently treated as DTH pile installation.
Notes: DTH = down-the-hole pile installation; SSL = sound source = level; dB = decibel; rms = root mean square; SEL = sound ure level.

Level A Harassment In conjunction with the NMFS
Technical Guidance 2018, in recognition of the fact that ensonified area/volume could be more technically challenging to predict because of the duration component in the new thresholds, we developed a User Spreadsheet that includes tools to help predict a simple isopleth that can be used in conjunction with marine mammal density or occurrence to help
predict takes. We note that because of some of the assumptions included in the methods used for these tools, we anticipate that isopleths produced are typically going to be overestimates of some degree, which may result in some degree of overestimate of Level A
harassment take. However, these tools offer the best way to predict appropriate isopleths when more sophisticated 3D
modeling methods are not available, and NMFS continues to develop ways to quantitatively refine these tools, and
will qualitatively address the output where appropriate. For stationary sources such as from impact and vibratory pile driving and DTH, NMFS
User Spreadsheet 2020 predicts the closest distance at which, if a marine mammal remained at that distance the whole duration of the activity, it would not incur PTS. Inputs used in the User Spreadsheet Tables 6 and 7, and the resulting isopleths are reported below Table 8.

TABLE 6NMFS TECHNICAL GUIDANCE 2020 USER SPREADSHEET INPUT TO CALCULATE PTS ISOPLETHS FOR
VIBRATORY PILE DRIVING
User Spreadsheet InputVibratory pile driving spreadsheet tab A.1 vibratory pile driving used 24-in piles temporary install/removal
16-in piles removal
lotter on DSK11XQN23PROD with NOTICES1

Source Level RMS SPL
Weighting Factor Adjustment kHz
Number of piles within 24-hr period
Duration to drive a single pile min
Propagation xLogR
Distance of source level measurement meters +

161
2.5
4 30
15
10

24-in plumb/batter piles permanent install
161
2.5
4 30
15
10

161
2.5
4 30
15
10

TABLE 7NMFS TECHNICAL GUIDANCE 2020 USER SPREADSHEET INPUT TO CALCULATE PTS ISOPLETHS FOR IMPACT
PILE DRIVING
User spreadsheet inputimpact pile driving spreadsheet Tab E.1 impact pile driving used 24-in piles permanent Source Level Single Strike/shot SEL
Weighting Factor Adjustment kHz
Number of strikes per pile

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