2008-04-15_REVISION - M1980244 ‎(336)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 4/15/2008
• Doc Name: Teller County Vol.1, Attachment 8, Noise Analysis Report
• From: CC&V
• To: DRMS
• Type & Sequence: AM9
• Media Type: D
• Archive: No

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IV. NOISE ASSESSMENT
A. APPROACH
A maximum measured noise emission (associated with a combination mining shovel and truck working in
tandem) of 82.6 dB(A) was selected to review noise profiles associate with the MLE and key receptor
sites. This maximum measured noise emission can then be used to determine the noise reduction for
any combination of noise barrier design and distance to an important receptor. The height of the source
of noise on a piece of equipment relative to the height of barrier and the distance from the source to the
barrier determines the noise reduction. For example, a Hitachi 5500 shovel's engines and cooling fans
are about 18 ft. above grade while the engine and cooling fan on a CAT D-10 dozer are about 8 ft. above
grade. Thus, an approximate 30 ft. high berm will be more effective in shielding the noise of a CAT D-10
dozer than a Hitachi 5500 shovel but effective for both pieces of equipment. Another factor controlling the
performance of a noise barrier is the distance between the barrier and the noise source; the closer the
noise source is to the barrier the more noise reduction provided by the barrier. The calculations to
determine the noise reduction provided by the berm use the Maekawa equation and have proved to be
reasonably accurate when the magnitude of the noise reduction is no greater than 25 dB. In this analysis,
all berm or barrier noise reduction values have been limited by the computer program, to not exceed 24
dB in any %3 octave band. This is a conservative approach in predicting the effectiveness of a noise
barrier.
When calculating the noise reduction due to distance, no additional noise reduction has been added for
the absorption of the sound by the atmosphere or vegetation, which is also a conservative assessment
approach. It is also assumed that the wind is calm and the effects of an up-slope or down-slope wind has
not been considered in the calculations.
When there are no obstructions between the source and receptor and when the distance from the source
is more than 100 ft., the following dB adjustments can be applied:
¦ Every time the distance is doubled or halved, the noise level is calculated to change by 6 dB. Going
from 100 ft. to 200 ft. reduces the noise by 6 dB and conversely in the other direction.
¦ Increasing the distance by a factor of 10 such as going from 100 ft. to 1000 ft. reduces the noise by
20 dB and conversely.
All noise values expressed as dB(A) are the maximum noise values for each piece of equipment and
depicts full operating speed. Noise reductions in the order of 10 dB(A) or more will occur when the
equipment engine speed or load is decreased.
Eight noise receptor sites were selected for detailed noise analysis. The distances from MLE activities to
these locations range from 1245 ft. to 5916 ft. The locations and distances for each site are shown on the
attached site map. For each receptor site, a topographical cross section has been prepared showing the
site and the closest mine activities area. These are presented on cross section sheets Acoustic A-A thru
Acoustic H-H. A detailed description of each site line follows.
1. Receptor Site A-A
Located in Section 29 on the east side of CR84. From the site, the distance is 1450 ft. in the
northwesterly direction to the Main Cresson Mine. Also, noise measurements had been taken at this
site in the winter of 2004 and included in the 2004 ECME report. This receptor is a seasonally
occupied vacation cabin.
2. Receptor Site B-B
Located in Section 21 on the northwest side of CR831. From the site, the distance is 2230 ft. in the
northwesterly direction to the East Cresson Mine (Altman) and backfill area of the MLE. This
receptor is a seasonally occupied residence.
3. Receptor Site C-C
Located in the western portion of Section 15. From the site, the distance is 5916 ft. in the westerly
direction to the East Cresson Mine. This receptor is a seasonally occupied cabin.
Rev # EDI Job No. C3616
Page 11 of 17
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