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i• <br />A 'BRA ECH 8120 N. Sheridan Boulevazd, Suite 304A,.Westminster, CO 80003-6140 <br />The Vibration Monitoring Experts <br />303-429-1996 FAX 303-429-1997 <br />PIKES PEAK MINING COMPANY <br />GROUND VIBRATION ATTENUATION STUDIES <br />GLOBE HILL, IRONCLAD AND CRESSON MINING AREAS <br />May 10-12, 1993 <br />EXECUTIVE SUMMARY <br />Vibra-Tech Engineers, Inc. monitored five production blasts and one <br />test blast at Cripple Creek and' Victor Mining Company operations <br />near Victor, Colorado. All. data and analyses are attached to this <br />report. A Scaled Distance of 34.2 is recommended to not exceed a <br />peak vibration level of 0.50 inches per second. This is a worst <br />case Scaled Distance analysis based on forty vibration readings of <br />typical production blasts. The recommendations are more <br />conservative than the Cresson analysis. It is likely that <br />• vibration levels created by blasting in the Cresson area will be <br />considerably less than the predicted maximums using the Scaled <br />Distance of 34.2. <br />SD= D <br />where: SD is Scaled Distance <br />D is Distance in feet <br />W is maximum charge weight per 8 millisecond delay period <br />The recommended Scaled Distance of 34.2 is conservative and a high <br />degree of statistical confidence can be placed in the values <br />calculated. Below is a table of maximum charge weights per delay <br />at given distances based on the recommended Scaled Distance of <br />34.2. <br />Distance Charge Weight/Delay <br />(FT) (#/Delay) <br /> 500 214 <br />l <br />1000 <br />855 <br /> 1500 1924 <br />~. 2000 3420 <br /> 2500 5344 <br />1 <br />