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investigations are unnecessary to assure that offsite damage caused by crushing operations will <br />be prevented. <br />The Division has considerable experience in similar gravel pit proposals where the potential for <br />mining and processing operations to cause damage to offsite structures has been evaluated. <br />Due to the fact that crushing operations will be at least 450 feet from the nearest home and <br />tree farm, and that ground vibrations rapidly attenuate with distance, the Division believes that <br />the potential for structural damage to nearby homes caused by crushing operations at the site is <br />essentially non-existent. Considerable research has been done to correlate vibrations from <br />single events with architectural and structural damage. According to the US Bureau of Mines <br />"safe level" blast criteria, vibrations below 2.0 in/sec measured in peak particle velocity (ppv) <br />produce virtually no risk of structural damage to buildings. Architectural damage (cracks in <br />plaster and drywall) could occur during events that produce peak particle velocities greater than <br />.5 in/sec. Continuous vibration levels greater than 0.2 in/sec ppv could produce some risk of <br />architectural damage, and levels greater than 0.4 in/sec ppv could produce some risk of minor <br />structural damage. Vibrations caused by most mining and construction activities would be <br />considered continuous, and therefore present risks of architectural and structural damage at <br />levels lower than those of single events, such as blasting. Vibrations caused by construction and <br />mining equipment (crushers, dozers, loaders) are not likely to exceed 0.1 in/sec ppv near the <br />source. Additionally, the intensity of ground vibrations attenuate quite rapidly as distance from <br />the source increases, so any vibrations caused by crushing operations will likely be at least an <br />order of magnitude less at the permit boundary. A study conducted by Navcon Engineering to <br />assess the ground vibration impact of a rock crushing facility into an adjacent residential <br />community showed peak particle velocities of less than 0.002 in/sec (the approximate threshold <br />of human perception) at a distance of only 25 feet from the crushing unit. <br />The Division has determined that the site specific conditions do not justify any requirement for the <br />operator to submit a geotechnical stability analysis to demonstrate that vibration from crusher and <br />equipment operation at the site will not adversely affect off-site structures or the Santee tree farm. <br />B. ISSUES NOT WITHIN THE JURISDICTION OF THE DIVISION AND BOARD <br />1. The proposed Gravel Pit will substantially degrade the value of the neighborhood for residential <br />and agricultural uses. All of the Neighbors live in close proximity to the proposed Gravel Pit and <br />would suffer degradation of quality of life and diminution in value of their property..." <br />Division of Reclamation Mining and Safety (DRMS) Response: <br />The jurisdiction of the Board and DRMS does not extend to land use decisions, visual or <br />economic impacts, noise, traffic, dust not caused by eroding berms or spoils piles, or other <br />Page 6 of 7