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<br /> <br />1 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br /> <br />The protection of surrounding property owners in the Castle Rock azea has been a priority of <br />CMI at their Ditmars operation and will remain a priority at the Castle Rock Quarry operation. <br />CMI has not had an accident due to blasting at the Ditmars location, and has received the Joseph <br />Holmes Safety Award for no lost-time injuries. In addition, there aze no complaints on file with <br />the Douglas County Sheriff's Office or any other government agency, of which we are aware, <br />regarding blasting noise, vibration, or property damage. Each blast is carefully planned to limit <br />the area of influence to the azea of the blast. <br />The blasts to occur at the Castle Rock Quarry will be very similar to those at the Ditmars Quarry. <br />All detonations of explosives at the Castle Rock Quarry will be monitored by the contractor. <br />This ongoing monitoring program will help the blasting experts plan and limit the impact of <br />future detonations. <br />To demonstrate the limited area of influence which blasting has, monitoring data from the <br />Ditmars Quarry for the first quarter of 1995 has been presented in Appendix 5 (Blast Monitoring <br />Data). Six blasts were measured to determine vibration levels at various locations surrounding <br />the Ditmazs operation. Figure 3.F(1) is a seismic monitoring location map of the Ditmazs <br />operation. Measurements were taken as close as 1,000 feet away from the blast and as faz as 3/4 <br />of a mile from the blast (next to azea residents). Table 3.F(1) summarizes the results. <br />Table 3.F.1(1) -First Quarter 1995 Seismic Monitoring Results for the Ditmars Operation <br />Date Seismic Measurement <br />Distance from Blest Peak Particle <br />Velocity (io/sec) Probable Effects <br />2/10/95 1,500 feet by office trailer no reading none <br />2/17/95 N-E 1/4 mile between two houses .ol Less vibration than walking on floor <br />2!23(95 3f4 miles south no reading none <br />3/08/95 1000 feet, by office trailer .078 Equivalent to walking on the floor <br />3/13/95 1000 feet, by office trailer .O1 Less vibration than walking on floor <br />3/14/95 1000 feet, by office trailer no reading none <br />Included in Appendix 5 is a report written by a blasting consultant explaining in detail the <br />concepts of blasting. The report also includes a listing of Peak Particle Velocities and associated <br />effects to persons and property. In blasting, Peak Particle Velocity (PPV) is the measurement of <br />the maximum movement of particles of rock and soil. PPV is measured in inches/second. When <br />blast vibration is recorded by a seismograph, three mutually perpendicular sensors record particle <br />velocities in longitudinal (radial), transverse, and vertical axes. When looking at the blasting <br />results, the longitudinal and transverse axes aze the most important to compare in determining the <br />damage potential to surrounding structures. <br />According to the U.S. Bureau of Mines, PPV is the most practical descriptor of vibration as it <br />applies to the damage potential for residential structures. In 1983, the Office of Surface Mining <br />and Reclamation (OSMRE) established regulations conVOlling vibration at all surface coal <br />mining operations. Three optional methods for controlling vibration are allowed. These options <br />are listed on pages 4 and 5 of the blasting report. <br />21 <br />