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• (Page 2) MINE ID ~` OR PROSPECTING ID ,$ M-88-081 INSPECTION DATE 10/11/95 INSPECTOR'S INITIALS ACS OBSERVATIONS This report details observations made and discussions held during the second of two site inspections conducted during September and October of 1995. This inspection was conducted in response to complaints registered by citizens living near the mine. Rocky Conner was present for the inspection, representing East-West Mining Corp., Inc. Several nearby residents have complained about ground vibrations related to blasting. All blasts create ground vibrations. When an explosive is detonated in a borehole it creates a shock wave that crushes the material around the borehole and creates many of the initial cracks needed for fragmentation. Aa this wave travels outward, it becomes a seismic, or vibration wave. Excessively high ground-vibration levels can damage structures, such as houses. Small underground mines shoot relatively small blasts releasing insufficient energy to propagate ground motions that could cause structural damage, however, this can be verified rather easil.r through use of the scaled Distance Equation. The Scaled Distance Equation considers the two primary controlling factors related to ground vibration created by blasting: (1) the distance from a blast location to a potentially affected structure, and (2) the charge-weight of explosive or blasting agent to be detonated in any 6-millisecond period. The Scaled Distance Equation is an accepted method for control of blasting related ground motion, and is used in the Office of Surface Mining, ''Blasting Guidance Manual", the Explosive Regulations of the Colorado Division of Labor, and ie described in the Bureau of Mines, "Information Circular x`8925 (1983)". The operator will be required to submit the following information so that an analysis using the Scaled Distance Equation can be completed: 1. A description of the type of explosive or blasting agent in use at the site. 2. The type and time period of delay elements before the priming charge in the detonator. A description of the delay series for a typical blast. 3. The charge weight in pounds of explosive or blasting agent detonated per delay period. 4. The horizontal distance from the blasting location to the nearest house. The Reclamation Permit and citizen complaints indicate that this distance ie approximately 150 feet, and thin is the distance that will be used in the scaled distance analyses unless a more precise measurement of the distance is provided by the operator. This information must be provided to the Division as soon as possible, but in any case no later than the close of business on November 1, 1995. This information must be submitted in writing to: Allen Sorenson Division of Minerals and Geology 1313 Sherman Street, Room 215 Denver, cO 80203 For purposes of meeting the November 1, 1995 deadline, the operator may relay this information by phone to my voice mail at 866-4929, ext. 322. Once a maximum permissible charge weight per delay has been determined for this Bite, through use of the Scaled Distance Equation, the Division will require the operator to maintain a blasting record. An example blasting record form ie attached to this inspection report. The seismic section at the bottom of the example blasting form will probably not be applicable to this site. The Division will require that the operator maintain blasting record forme for each blast on file at the site, and to provide the blasting records for Division review upon request. Several complainants have expressed a concern with the potential for flyrock caused by blasting at the Phil Sheridan Bite. The operator reported that the shaft is now at a depth of 80 feet, and that the shaft ie covered at the collar at the time of blasting. As such, the potential for flyrock is eliminated. If any surface blasting operations are proposed in the future development of the mine site, adequate measures to prevent flyrock would be