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~. <br />!. <br />F <br />Introduction <br />Matheson Mining Consultants was retained by Seneca Coal Company to perform a <br />ground motion attenuation study of ground vibrations created by blasting in the 2-W area. <br />The primary point of concern in this area of the mine is the Meridian Oil Well, Dry <br />Creek Unit 3-22 with a 5.0 inch per second peak particle velocity limitation. Five <br />blasting seismographs monitored each of the ten test blasts. Each test blast was <br />composed of a single nine inch diameter drill hole loaded with twenty feet of 38/62 blend <br />of emulsion and anfo. Seismographs were positioned at varying distances from each test <br />blast. The resulting data sets were analyzed and used to determine distance and charge <br />weight relationships required for ground vibration regulatory compliance. The distance <br />studies predict statistically safe distances for any given charge weight per delay period <br />and peak particle velocity. <br />The procedure for the analyses performed on the test blasts is outlined in "Blasting <br />Guidance Manual", March 1987, published by United States Department of the Interior <br />Office of Surface Mining Reclamation and Enforcement. <br />The tests performed were designed to be conservative in nature. The intent of these <br />studies was to maximize ground motion. Typically in mine production blasting, <br />explosive energy is consumed by fragmentation and displacement of the rock mass. The <br />confined test blasts minimized fragmentation and displacement while maximizing ground <br />motion. <br />Instrumentation <br />Vibration records were collected with one Blastmate III and four MiniMate Plus digital <br />. blasting seismographs. These seismographs measure three orthogonal planes of ground <br />motion, transverse, longitudinal and vertical, and one channel of air overpressure. The <br />'- frequency response is 1.5 to 250 Hertz. All instruments have a valid annual calibration. <br />Copies of the calibration certificates are attached as Appendix I. Each vibration <br />recording is printed on a single sheet of paper with: Date/Time, Trigger Source, Range, <br />Record Time, instrument Serial Number, Battery Level, Calibration date and File Name <br />in the title block. The instruments are seismically triggered and record each channel <br />digitally at 1024 samples per second. <br />Fourier transforms of each of the three waveform components are calculated to determine <br />frequency response. Frequency versus particle velocity plow of each wave trace are plotted <br />on each record. The United States Bureau of Mines (USBM) and the Office of Surface <br />Mining, Reclamation and Enforcement (OSMREj regulatory criteria are plotted on each <br />vibration record. <br />Attached as Appendix R is an excerpt from the Biastmate III User's Manual describing the <br />specifications and function of the instrumentation and record processing. <br />• <br />• <br />• <br />2 <br />