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Eagle Mountain Major Gravel Operations <br />Table 2 - Results <br />Distance is in meters, noise/attenuation in dB. <br />High Level HSE Review <br />Case ...._ _.... i - <br />._.......__ ... - --- --- __ - I.._...._.._l i__ ._ `_'L._ ......'a_..._...._ __ `*.1_. . . <br />_ -------- <br />Receiver/Receptor distance from plant fence line 70' 100': 200' 300 `: 400 500 <br />_ <br />Equipment Noise Distance assumed from plant fence line in 17 17; 717. 17 17' 17' <br />meters . <br />Base sound level assumed at fence line 95; 951 95 95 y? Y <br />Attenuation due to distance 45 48 54, <br />__._._......___..... F 58? 60 ... 62 <br />Attenuation due to grass absorption (2.00 dB/30m) 55 7 13! 20(?27? 33 <br />_--..----I _.... .,i.... -- <br />.truck 94. 94: 94 94 94 94 <br />:Base sound level fora...diesel_ <br />. <br />- -- ------------ <br />Attenuation due to distance as noted above 45! 48' 54 58' 60 62 <br />?I ___ <br />Total' Theoretical Sound Level At Receiver Location (pl'ant 51.5- 47.5? 40.3 36: 3`4 32 <br />noise plus awoff:site dump truck). (note: if greater thaw 16'dB' <br />between plan-and traffic noise; 0 additive effect was added'.-- see <br />attachment 1) <br />It should be noted that theoretical sound calculations are based on various assumptions that are often difficult to <br />quantify. Calculations should be considered to be within +/- 10%, 3 - 5 dB. <br />Discussion of results and sensitivities. <br />Distance is the best mitigation for sound levels. Since attenuation due to distance follows the <br />inverse square law, the most significant reductions due to distance is in the near field. Distances <br />greater than 250 overall showed noise results less than 40 dB, therefore any additional attenuation <br />becomes insignificant and a lesser delta or change from anticipated existing noise levels. At 300 <br />in there are no longer additive affects from plant noise and dump truck off-site at the same <br />distance. This is without taking credit for grassland attenuation for the dump truck noise. <br />A sensitivity was done using 1 dB for grassland and compared to the 2 dB assumption. For a 70 <br />in distance to a receiver/receptor the difference was approximately 0.5 dB; 200 in the difference <br />was approximately 1 dB greater. Therefore, only the 2 dB assumption calculations are reported. <br />In assessing noise generation, construction equipment can be grouped into two categories, <br />stationary and mobile. Equipment noise can also be categorized as being either continuous or <br />impulse in nature. Stationary equipment is considered to operate in one location for one or more <br />days at a time; pumps, generators, compressors, screens, are typical examples of stationary <br />equipment. Mobile equipment includes machinery that performs cyclic processes such as the <br />bulldozers, scrapers, loaders, and dump trucks. Mobile equipment is required to be equipped with <br />backup alarms. These alarms can be automatic/self adjusting based upon background noise, or <br />manually adjusted (typically daily adjustment) with high alarm levels generally peaking at 107 <br />dB. Backup alarms are classified as an intermittent noise. <br />-4-