Laserfiche WebLink
Subsidence Evaluation for the <br /> Exhibit 60E Southern Panels, Apache Rocks West, & Sunset Trail Mining Areas Page 40 <br /> 13.0 POTENTIAL IMPACTS FROM LOCAL SEISMIC ACTIVITY <br /> Earth tremors have been recorded or felt by local residents in the Somerset area since the early <br /> 1960s. The tremors commonly are the result of coal mine bumps and rock bursts, which are <br /> spontaneous releases of strain energy in highly stressed mined/caved coal and rock. In the <br /> Somerset Mine area before closure, the bumps and rock bursts were common in room-and-pillar <br /> mining areas where stresses concentrated within isolated pillars and blocks of coal (called bump <br /> blocks). Earth tremors have continued sporadically in the Somerset Mine area since the mine was <br /> closed in the 1980s. <br /> Tremors generated by bumps and rock bursts in the Somerset Mine area attain magnitudes that <br /> have shaken structures in the West Elk Mine area and have sometimes been felt by West Elk Mine <br /> personnel. These local tremors may affect,to a minor degree,underground workings, landslide or <br /> potential rockfall areas, particularly during prolonged periods of increased precipitation. It is <br /> noteworthy, however, that the Rulison nuclear shot in 1969, which produced a tremor with a <br /> Richter magnitude of 5.2 (the magnitude of energy released was many times greater than the <br /> magnitudes of any recorded bump or rock burst), did not affect the Somerset Mine. To our <br /> knowledge the Rulison nuclear shot did not trigger any landslides or rockfalls, nor did it impact <br /> reservoirs, ponds, or streams in the Southern Panels, Apache Rocks West, or Sunset Trail mining <br /> areas. <br /> 831-032.912 Wright Water Engineers, Inc. <br /> December 2020 <br />