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i.o immoDucTicK <br /> The Bear Coil Company has been mining coal in its W3 mine in Somerset, <br /> Colorado since the early 1980's. To date that mining has been entirely within <br /> the "C" seam. It is the intention of Bear Coal Company to begin mining the "B" <br /> seam located some 35 to 40 feet lower in the section at the same mine site. <br /> Therefore, the "B" seam mining will not require any changes in the permit <br /> boundary for the mine. It is our understanding that the Colorado Mined Land <br /> Reclamation Division is concerned about the potential for cumulative impacts from <br /> subsidence in both the "B" and "C" seams at this site. This report presents the <br /> results of a study of the surface subsidence impacts of the proposed multi-seam <br /> mining. <br /> Based upon the mining which has actually occurred within the "C" seam and <br /> that mining proposed within the "B" seam, the maximum anticipated subsidence from <br /> the combined effects of both seams is estimated to be approximately 5.4 feet. <br /> This occurs under relatively shallow cover near the outcrop in the extreme <br /> northwestern portion of the mine. Typical amounts of subsidence over the more <br /> southerly panels range from 1.5 to 3.5 feet. Horizontal ground strains have been <br /> estimated and were found to range from a compressive strain of 1.0 percent to a <br /> tensile strain of 1.2 percent. The majority of the surface above the mine <br /> consists of a rugged, steeply sloping topography. The predicted amount of <br /> subsidence in this type of envirormnent is not sufficient to produce grade <br /> reversals or any other serious alteration of the existing drainage. Tensile <br /> ground strains are sufficient to produce surface tension cracks in some <br /> locations. These tension cracks will temporarily alter the state of stress in <br /> the soil and rock and increase the amount of moisture entering the subsurface <br /> during storms. guile open these tension cracks may present a minor hazard to <br /> i <br />