Condit Dam Removal Condit Dam Removal - Access Washington

Condit Dam Hydroelectric Project
Final Supplemental EIS
• Sound waves propagate from each source according to hemispherical spreading.
• No attenuation due to ground attenuation from vegetation was assumed.
• The inventory of equipment (noise sources) that would be used during each phase of
construction was assembled based on the scope of work presented in the Project
Description document.
• No octave-band sound frequency data were available for the construction equipment
to be used at the project site. In accordance with ISO Standard 9613-2 “Attenuation
of Sound During Propagation Outdoors: A General Method of Calculation” the
reference noise levels for these sources were assigned to the 500 hertz (Hz) octave
band for purposes of estimating atmospheric absorption.
• All noise sources were assumed to be operational and emitting noise continually
during daytime hours.
Table 4.8-3 summarizes calculated cumulative noise levels at specific distances from the
Proposed Action due to noise generated by construction activities.
Table 4.8-3
Noise Modeling Results
Action
Pre-Dam Removal Activities
Hardware Removal & Tunneling
Dam Breaching & Removal
Concrete Dam Demolition
Concrete Removal, Storage, Disposal
Distance
(miles)
SUMMER
Cumulative noise level
(dBA) a
WINTER
Cumulative noise level
(dBA) a
1/8 34 35
1/4 28 28
3/8 24 24
1/2 21 22
5/8 18 19
3/4 16 18
7/8 15 16
1 14 15
1/8 34 34
1/4 27 28
3/8 23 24
1/2 20 21
5/8 18 19
3/4 16 17
7/8 14 16
1 13 14
1/8 35 35
1/4 28 29
3/8 24 25
1/2 21 22
5/8 19 20
3/4 17 18
7/8 15 16
1 14 15
4.8-7