2010-06-22_PERMIT FILE - M2010019

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Eagle Mountain Major Gravel Operations r I A Table 2 - Results Distance is in meters, noise/attenuation in dB. High Level HSE Review -- -_ - - - - - - - -..__?._ - 21 511 Case -??C L 6i 3 -- - - - - 1! Receiver/Receptor distance from plant fence line --- - --- --- - - -- ---- 500 70i 100; 200a(?300J 400; I - _ - _ - - __- - - _ - -- -- Equipment Noise Distance assumed from plant fence line in 17? 17 17 17 17? 417 'meters Base sound level assumed at fence line 95? 95 ; 95 95 951 - 95, --------- - ----- Attenuation due to distance 451 4848 S4; F- . _._.__ ._.__? Attenuation due to grass absorption (2.00 dB/30m) ! 5 -7 j -- 13 i 20, 27 1 33 i Base sound level for a diesel truck leve 94 9494 9?4?94?I _---,- _-...___._._._._ ! Attenuation due to distance as noted above 45 48 54;54; ------_._60! `fotat''I?hclotelical Sound l,rvel nt Kicci?er 1 oeabion (plant ? 51 51 -17,:5 ?rY?11 l? 3(ry? 3'1?' ?"?I ,noise-,plus an,off sltc dump tract.) {note-it ?zr(?. ter than, 6 ,.: ' - ` (113`x" cc 6i ct''As adiied s o''d traffic noix, Q additi?.tl e U?l??een;ptan a -attachment 14'- l It should be noted that theoretical sound calculations are based on various assumptions that are often difficult to quantify. Calculations should be considered to be within +/-10%, 3 - 5 dB. Discussion of results and sensitivities. Distance is the best mitigation for sound levels. Since attenuation due to distance follows the inverse square law, the most significant reductions due to distance is in the near field. Distances greater than 250 overall showed noise results less than 40 dB, therefore any additional attenuation becomes insignificant and a lesser delta or change from anticipated existing noise levels. At 300 in there are no longer additive affects from plant noise and dump truck off-site at the same distance. This is without taking credit for grassland attenuation for the dump truck noise. A sensitivity was done using 1 dB for grassland and compared to the 2 dB assumption. For a 70 m distance to a receiver/receptor the difference was approximately 0.5 dB; 200 in the difference was approximately 1 dB greater. Therefore, only the 2 dB assumption calculations are reported. In assessing noise generation, construction equipment can be grouped into two categories, stationary and mobile. Equipment noise can also be categorized as being either continuous or impulse in nature. Stationary equipment is considered to operate in one location for one or more days at a time; pumps, generators, compressors, screens, are typical examples of stationary equipment. Mobile equipment includes machinery that performs cyclic processes such as the bulldozers, scrapers, loaders, and dump trucks. Mobile equipment is required to be equipped with backup alarms. These alarms can be automatic/self adjusting based upon background noise, or manually adjusted (typically daily adjustment) with high alarm levels generally peaking at 107 dB. Backup alarms are classified as an intermittent noise. -4-