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much as possible. Recording Locations and distances to the nearest shot hole were surveyed by <br />• Seneca for MMC. Recording locations were limited due to topography, dense oak brush, soil <br />stockpiles, or mined areas. An effort was made to place the seismographs in virgin earth or on a cut <br />when possible. No recording locations were placed on fill. <br />Two "lines" of seismographs were placed between the Yoast pit and the nearest culture (please see <br />map in Appendix III). The recording line for the first shot extended southwest from the shot <br />towards the nearest residence (Brian Valora). The recording line for the second and third shots <br />extended northwest from the pit towards the Gary Valora residence. A seismograph was placed at a <br />300 foot distance from each of the three shots and a seismograph was placed at an approximate <br />5000 foot distance from each of the three shots. A seismograph was placed at the nearest residence <br />(Brian Valora) for all three shots. When possible, a seismograph was placed at a point of concern: <br />BE6516 on north end of pond dam northeast of Brian Valora's residence for shot 1, BC7817 north <br />of Brian Valora's trailer for shots 1, 2, and 3, BC7092 at Leonard Yoast's house for shot 1, and <br />BA5738 at Gary Valora's house for shots 2 and 3. <br />The peak particle velocity measured at each location is used in a least squares linear regression <br />program (in Excel) to provide asite-specific statistical analysis of ground motion for the Yoast <br />Mine area. The United States Bureau of Mines (USBM) and the federal Office of Surface Mining <br />and Reclamation Enforcement (OSMRE) specify this method of determining safe distances to <br />events causing ground vibration. All recommendations in this report are based on USBM, <br />OSMRE, and Colorado Division of Minerals and Geology criteria. <br />• RF.CI TI .TS <br />The ground motion analysis data set, preceded by a table summarizing the data, is found in <br />Appendix IV. The vibration recordings are ordered by shot and distance and aze best referenced <br />to the data table by time and instrument number. Thirty-two vibration records comprise the data <br />set for the ground motion analysis. The USBM and OSMRE variable particle velocity vs. <br />frequency criteria is plotted on each vibration event report. The upper line represents the threshold <br />level for possible sheeVock damage, while the lower, dashed line represents the threshold level for <br />possible plaster-on-lath damage. <br />The ground motion analysis is found in Appendix V and includes a page showing the curve and <br />derived equation, a page of regession statistics, a description of the statistics, scaled distance vs. <br />peak particle velocity tables for 50%, +95%, and +99% confidence levels, and a charge weight vs. <br />constant 1.00 ips peak particle velocity and constant distances table. The +95% curve is two <br />standazd deviations from the mean (50% curve) and is the curve specified for use by the USBM and <br />OSMRE. <br />For the Yoast attenuation study, the correlation coefficient ~rz~ is 0.966, which indicates an <br />excellent fit of the data (1.0 is perfect). The +95% confidence equation is PPV = 226.6 * (SD)-'.ez , <br />where PPV is the peak particle velocity in inches per second, SD is the scaled distance, 226.6 is the <br />• <br />6 <br />