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(~'T ATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY III III III III IIII III <br />Departmem of PJa coral Resources 999 <br />1313 Sherman SI., Room 215 I`~ <br />Denver, Colorado 80203 I <br />Phone: 1303) 865-3567 <br />FAX (3031 832~~I106 <br />NATU~ <br />RESOURCES <br />DATE: December 7, 1995 Roy Romer <br />Governor <br />TO: File No. M-88-081 la mes S. Lochhead <br />/ Exec wive Dirttmr <br />/ ~ Michael B. Wng <br />FROM: Allen Sorenson ~,~~ ~ Division Director <br />RE: Evaluation of the Potential for Impacts to be Caused by <br />Blasting Related Ground Motions, East-West Mining Corp., Phil <br />Sheridan Lode <br />The simp:Lest method by which to evaluate blasting related ground motions <br />is the Scaled Distance Equation. Because the Scaled Distance Equation <br />does not consider site-specific geologic variables, it is designed to be <br />very con:aervative, i.e., the Scaled Distance Equation is very restrictive • <br />in terms of the amount of explosive that may be detonated, and is very <br />protective of nearby structures. <br />The Office of Surface Mining has established limitation on the peak <br />particle velocity (a measure of ground motion) that may be caused by <br />blasting at various distances from the blasting location. The maximum <br />allowable: peak particle velocity for structures within 300 feet of a <br />blasting location is 1.25 inches per second. If blasting is conducted in <br />accordance with the Scaled Distance Equation, the peak particle velocity <br />is deemel9 to be within this limitation. The Scaled Distance Equation <br />relates the parameters of charge weight and distance. Reducing the charge <br />weight, or increasing the distance, results in a smaller ground vibration. <br />The maximum weight of explosives to be detonated within any 8-millisecond <br />period mely be determined by the Scaled Distance Equation: <br />W = (D/Ds)z <br />Whex•e: W = the maximum weight of explosives, in pounds, that can <br />be detonated in any 8-millisecond period; <br />D = the distance, in feet, from the blast to the nearest <br />dwelling, school, church, or community or institutional <br />building; <br />DS = the Scaled Distance Factor. <br />• <br />