2010-06-22_PERMIT FILE - M2010019

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Eagle Mountain Major Gravel Operations High Level HSE Review Assurance that the asphalt plant will not be installed in the future. Though withdrawn from the current conditional use permit application, the concern is that new hazards will be introduced and the facility will not be designed adequately to take care of the environmental and health issues and potential drainage/contamination issues. NOISE ISSUES General. Plant fence line acceptable values can vary significantly. Fence line monitoring is often required for reduction of noise pollution to neighbors during both construction and operational phases of industrial facilities. Operating plant fence line limits are often determined by local or regional governmental requirements. Remote locations in environmentally sensitive areas often require research into the affects of various noise exposures on wildlife populations. Engineering controls within the facility are the best mitigation to reduce the noise at the initiating source and therefore the fence line. Attenuation through distance is the best mitigation for fence line noise that is going off-site. The loudness, or decibel level (abbreviated dB) of a sound decreases inversely with the distance from the source. In other words, the farther the receiver is from the source, the less sound there is at the receiver. Other attenuation factors include terrain and movement through air. Presence of Trees, Shrubs and Other Foliage. The foliage surrounding the area is dense in some places, and can provide another source of attenuation. This area of noise attenuation quantification is not well defined. The literature available on this subject suggests that attenuation due to plantings corresponds somewhat to visibility through the same, and that for dense foliage attenuation can vary between 2 - 5 dB/100 feet. During the summer months when activities on the site will be the greatest, trees will provide the most effective barrier to sound propagation because of their leaves. For this study, we will neglect attenuation caused by trees and tall foliage in order to arrive to account for the fact that it is anticipated that activity will continue during the winter months when the trees have no leaves. For the purposes of this study, additive effects from noise are considered as illustrated in Appendix I. Basic sound principles and the adding of sound power levels/dB through a logarithmic scale show that adding two like sound levels gives a 3 DB increase. For esample, two pieces of equipment each at 70 dB provide a combined dB of 73. When the delta between two sources is greater than 16, the additive affect is negligible. For example, a 70 dB and a 53 dB source are combined, the additive is 70 dB. Elevation and Terrain. The worst case sound level at any receiver/receptor location will be when the equipment is at an elevation to the receiver/receptor. The ground is a reflective medium. For purposes of estimating sound levels at ground level and elevations, The Engineering Equipment and Materials Users Association (EEMUA) Publication No. 140 can be used as a guideline for calculations. Noise sources are to be considered small sources and a directivity index is not required. To account for ground reflection, hemispherical radiation calculations are used to model sound propagation at ground level equipment. Spherical radiation calculations are used to model sound propagation if at elevation from the receiver/receptor. The hemispherical radiation calculations assume a hard reflective surface. Large expanses of grass have been shown to provide absorption and provide attenuation. Attenuation will vary between 1- 3 dB/30 in depending upon the frequency of the noise source. For this study, the assumption for grassland is considered to be at 2 dB/30 in. 2 dB was chosen to as the average, or -2-