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• The coal deposits along Hay Gulch lie in Cretaceous rocks. As a result <br />of regional uplift and constant erosional processes, the formations with <br />Cretaceous rocks are characterized by somewhat steep topography along <br />Hay Gulch. Hence, the coal is exposed in an essentially narrow canyon <br />on the faces of what Colorado characterizes as naturally occurring <br />highwalls, formed over centuries. Due to the increasing overburden <br />thicknesses in this area with these outcrops, most of the portal areas <br />along Hay Gulch lie along the steep outcrop of the coal, with the <br />development of portals into the coal seam. <br />The result of this method of extracting coal is the development of <br />benches, roads and other surface operation facilities in the somewhat <br />steep topography. The portal areas used by the Peacock Coal Mine have <br />been constructed from the spoil removed from the face-up areas. The use <br />of spoil in constructing a stable fill in the portal areas reduces the <br />volume of material removed from the face. Hence there 'is less <br />disturbance to the affected surface area. Reclamation of these areas to <br />• the elimination of the face-up or highwall could be environmentally <br />unsound and counterproductive to reclamation requirements. <br />Complete elimination of a "highwall" in an area with average slopes <br />greater than 30° by backfilling to the angle of repose could create <br />several problems. Winter snow melt or intense surtoner thunder showers <br />could result in excessive erosion on the steep slopes. Moreover, the <br />static safety factor of 1.3 would be difficult to achieve. On the other <br />hand, backfilling to a lesser angle, such as 2 horizontal to 1 vertical <br />or 3 horizontal to 1 vertical, would be impractical because there would <br />not be enough material from the original cut to achieve the desired <br />slope. An attempt to reduce the face cut by blasting material from <br />above the cut would probably cause slumping of material from the entire <br />height of the area. Hauling the needed backfill material in from other <br />sites would only create additional surface disturbance. <br /> <br />2.05-28 <br />