Federal Register - September 1, 2021
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Source: Federal Register
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Federal Register / Vol. 86, No. 167 / Wednesday, September 1, 2021 / Notices TABLE 4PROJECT SOUND SOURCE LEVELS AND USER SPREADSHEET INPUTS
Activity 3
Source level dB RMS 1
Type of source
Vibratory pile driving
13-inch polycarbonate pile removal
16-inch concrete pile removal
16-inch concrete pile clipping with +3dB adjustment for two simultaneous pile clippers.
16-inch concrete pile removal using hydraulic chainsaw underwater chainsaw.
Wire saw for caisson cutting
Stationary Stationary Stationary Stationary
source, source, source, source,
non-impulsive, non-impulsive, non-impulsive, non-impulsive,
Duration of sound production hours 2
Transmission loss coefficient
continuous continuous continuous continuous
152
154
147
150
0.1667
0.42
0.42
0.42
15
11.7
15
15
Stationary source, non-impulsive, continuous
150
0.83
15
Stationary source, non-impulsive, continuous
156
1.7
15
1 All
of these sound source data for use in the Level A and B harassment threshold modeling were calculated from acoustic data found in the 2020 San Diego Noise Compendium NAVFAC SW, 2020; the only exception is the vibratory hammer source level which was sourced from the City of Seattle Pier 62 Project Greenbusch Group, 2018.
2 The User Spreadsheet inputs assumed 5 piles will be removed within a single 24-hour period using data from the Navys Compendium NAVFAC SW, 2020.
3 All activities utilized a weighting factor adjustment kHz of 2.5.
For this project, we modeled sound propagation using the practical spreading value of 15 for transmission loss for all pile removal methods, except for the removal of the 13-inch polycarbonate piles. For this, 11.7 was
used as the transmission loss coefficient as this value was a calculated measure from recorded data that was fit with a logarithmic trendline during the clipping of a 13-inch round concrete pile using small pile clippers in
February 2017 at the old Fuel Pier NAVFAC SW, 2020. The above input scenarios lead to PTS isopleth distances Level A harassment thresholds of less than 1 meter for all methods and piles Table 5.
TABLE 5MODELED AND EXPECTED LEVEL A AND B HARASSMENT ISOPLETHS USING TWO METHODS FOR THE PILE
TYPE AND REMOVAL METHOD METERS
A
Projected distances to Level A harassment isopleth 3
Pile information
Removal method MF
13-inch polycarbonate pile ..
14-inch, 16-inch concrete piles.
14-inch, 16-inch concrete pile 1.
14-inch, 16-inch concrete pile.
14-inch, 16-inch concrete pile.
14-inch, 16-inch concrete pile.
B
Projected distances to Level B
harassment isopleth 5
PW
Practical spreading loss model
OW
Real-time data
One pile clipper
One pile clipper
0.0
0.0
0.0
0.0
0.0
0.0
5 423
350
145
5 250
Two pile clippers
0.0
0.0
0.0
229
5 250
Underwater chainsaw
0.0
0.1
0.0
5 229
45
Diamond wire saw
0.1
0.7
0.0
5 575
350
Vibratory hammer
0.1
0.9
0.1
5 311
4
MF = mid-frequency cetaceans, PW = phocid pinnipeds, OW = otariid pinnipeds.
1 The Navy added an adjustment of +3 dB to the noise of a single pile clipper 147 dB RMS re 1Pa and increased to 150 dB RMS re 1Pa where two clippers are used simultaneously Kinsler et al., 2000. This adjustment is consistent with NMFS guidance for simultaneous sound sources.
2 All sound sources were taken from the Compendium of Underwater and Airborne Sound Data during Pile Installation and In-Water Demolition Activities in San Diego Bay, California San Diego Noise Compendium; NAVFAC SW, 2020, with exception of the vibratory hammer which was sourced from the City of Seattle Pier 62 Project Greenbusch Group, 2018.
3 Because of the small sizes of the Level A harassment isopleths as determined by NMFSs User Spreadsheet Tool and the mitigation methods implemented during this project, neither NMFS nor the Navy expects Level A harassment and, therefore, take to occur.
4 No information available.
5 Designate the most conservative isopleths NMFS will use for the subsequent Level B take analyses and Level B harassment impact zones.
khammond on DSKJM1Z7X2PROD with NOTICES
Level B Harassment Zones Transmission loss TL is the decrease in acoustic intensity as an acoustic pressure wave propagates out from a source. TL parameters vary with frequency, temperature, sea conditions, current, source and receiver depth, water depth, water chemistry, and bottom composition and topography.
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The general formula for underwater TL
is:
TL = B Log10 R1/R2, where:
TL = transmission loss in dB
B = transmission loss coefficient; for practical spreading equals 15
R1 = the distance of the modeled SPL from the driven pile, and R2 = the distance from the driven pile of the
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initial measurement
The recommended TL coefficient for most nearshore environments is the practical spreading value of 15. This value results in an expected propagation environment that would lie between spherical and cylindrical spreading loss conditions, which is the most appropriate assumption for the Navys activity in the absence of specific
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