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~ 11 1 IIIIIIIIIIIII III ,~ STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Depanmenl of Natural Resources 1317 Sherman 51., Room 215 y` Denver, Colorado 80203 Il y Phone: 13031 866-3567 Il FAS~ p(131 832-8106 DEPARTMLIVT OF NATURAL September 1, 1998 RESOURCES Roy Romer To: Anthony J. Waldronn, James Stevens enveinor ~~ Wmrs 5 Lochhead From: James Dillie t.ec°'Ive Dlrr°°' Michael 8. Long Di~~ision DveUOr Re: Review Blasting Report, Pinon Mine Site, M-97-094 Per your request, I reviewed [he blasting report submitted by Geotek & Associates, Inc. regarding mining operations at the referenced site. As noted in the report, the operator plans to only use 1 pound of explosive per drill hole. Each hole will be stemmed with at least 2 feet of drill cuttings. The blast pattern will include an 8 millisecond delay pet shot. The report correctly calculated [he anticipated peak particle velocity of the proposed blasting events and accurately described the anticipated "airblast" measurements. The Division does not have a set of standards for blasting so, in the past, OSM blasting standards have been used. Extensive OSM research has shown that if peak panicle velocity (ground motion) is at or below 1 in/sec and air overpressure (airblastj is at or below 120 dBL, the probability of sttvctural damage to nearby structures is extremely low. These are the standards that are currently used. The anticipated ppv for this operation is calculated to be 0.033 in/sec for the nearest structure and 0.028 in/sec for the nearest well. Airblast is anticipated to be 114 dBL. In my opinion, the proposed blasting operation will not adversely affect any noted nearby structures. If conditions change ([he operator decides to use more explosives etc.), [he operator should be required [c submit a revised blasting report.