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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eJ' d-, 1j2. Noise Berms
After the growth medium has been moved to the permanent stockpile storage areas the dozer or
dozers will return to the site and prepare the approximate 30 ft. high noise berm that will shield the
noise from the equipment. One CAT D-10 dozer can work to within 1900 ft. of the nearest receptor
and not exceed the 50 dB(A) noise limit. Two dozers working simultaneously close to each other and
at maximum power can operate to within 2600 ft. of the nearest receptor and not exceed the 50 dB(A)
noise limit. It is highly improbable that two dozers would be pointing in the maximum noise direction
simultaneously. Most of the time only one dozer will be used for berm construction.
3. Blast Hole Drilling
Blast hole drilling will start once the noise berms are in place. There will be locations where the
distance to the nearest receptor is such that the 50 dB(A) nighttime limit will not be exceeded even
when there is no berm such as Site C-C where the distance is 5143 ft.
Noise measurements were taken on February 3, 2004 of the noise emissions from a cluster of 4 rock
drills in operation at the CC&V Mine. This cluster of 4 drills produced a noise level of 80.8 dB(A) at
100 ft. In June of 1988, E. D. I. conducted noise measurements of rock drills at an operating rock
quarry located west of Denver. These data are presented in Table 5.
Table 5
Rock Drill Noise Emission 1988 Data
Test No. DB A Test Distance - Ft. DB A 100 Ft.
1 77 200 83
2 70 400 82
3 59 800 77
4 78 100 78
5 68 500 82
6 68 600 84
7 67 700 84
8 68 800 86
Average 82
The measurements taken in 1988 are in close agreement with those taken at the CC&V mine in 2004
considering that rock drill manufacturers have addressed noise emission and implemented noise
control in their product design.
The constructed berms will reduce the rock drill noise by at least 8 dB(A) or greater depending upon
the elevation of the receptor. An 8 dB(A) reduction in the noise of four drills will put the 55 dB(A)
contour at 800 ft. and the 50 dB(A) contour at 1400 ft. Without any berms, the 55 dB(A) noise
contour distance would be 2000 ft. and the 50 dB(A) noise contour distance would be 3500 ft.
However, at a distance of 3500 ft., the absorption of sound by the atmosphere would reduce the
distance of the 50 dB(A) contour to about 3000 ft.
After a blast hole pattern has been drilled, the rock drills move away from the drilled areas and the
holes are filled with explosives and detonators transported to the site in the explosives truck. The
explosives truck is a relatively small noise source compared to the rock drills and produces less than
65 dB(A) at 100 ft. and 55 dB(A) at a distance of less than 500 ft. The transporting and loading of
explosives is a daytime operation.
4. Mining General Discussion
a. First Bench Level
During the first bench cut the rock drills will be at the surface and behind the noise berm. Four
rock drills will produce 50 dB(A) at 1400 ft. when they are working directly behind the berm.
When the rock drills are further away from the berm there is the combined effect of the berm and
distance and a noise reduction of more than 10 dB(A) will occur.
Rev # EDI Job No. C3616
Page 14 of 17
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