Laserfiche WebLink
Subsidence Evaluation for the <br />Exhibit 60E Southem 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 />831-032.816 Wright Water Engineers, Inc. <br />October 2018 <br />