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RECLAMATION - BENCHES <br /> COAL BASIN - GEOLOGY/MORPHOLOGY <br /> As indicated in the Geo-Hydro report (1983): <br /> Morphological features of the area have been very much influenced by the <br /> harsh climate related to the exceptionally high altitude. Erosional processes <br /> significantly contributed to the rugged topography. Frequent avalanches <br /> continuously modify the surface features at numerous locations along the <br /> haul roads and at several mine benches. <br /> As indicated in the Permit Application ( Sec. III-G) <br /> • The Coal Basin is characterized by steep, erratic, deeply eroded terrain. <br /> Dips along the flanks of the anticline vary from 350 to nearly vertical in the <br /> lower Coal Creek drainages. <br /> • The vertical rise of ground within the basin is precipitious, ranging from <br /> 8,000' at the preparation plant area to 10,000' along the Huntsman Ridge. <br /> Areas of moderate terrain are rare, occurring only in the south part of the <br /> basin and in a few landslide and slumpage areas. <br /> • The Coal Basin is highly eroded. The erosion cycle probable dates from the <br /> end of the Eocene, some 36,000,000 years ago. It has been estimated that, <br /> assuming a fairly constant rate of erosion, some 15,225 tons of rock, <br /> including 29 tons of coal, are eroded out of the Coal Creek drainage system <br /> each year. Since the Eocene, over 548,082,800,000 tons of rock have <br /> eroded from the Coal Basin. <br /> • The principal formations of Coal Basin are Mancos Shale and the <br /> Mesaverde, although several zones of igneous dikes have been <br /> encountered, both on the surface and in underground development. The <br /> outcropping strata of the Mesaverde formation occur as a rim around the <br /> erosional basin, which is floored by impermeable Mancos Shale. <br /> • The outcropping strata in the Coal Basin differ in erosional properties but <br /> are, for the most part, highly erosive, particularly in the the case of the <br /> Mancos Shale, which floors most of the basin and is the most common unit. <br /> The center of the basin, which is floored by deformed and highly erosive <br /> Mancos Shale, is notably erratic. <br /> • Because the shale is easily eroded, it tends to be highly erratic. Moreover, <br /> several areas within the unit have been contorted by plastic deformation, <br /> 2 <br />