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1 . Background <br /> All of the Mid-Continent Mines were operating many years before <br /> reclamation law initiation in 1977 . This is verified by existing <br /> permit data, aerial photos and a wealth of other information. <br /> Five separate portal areas were constructed at elevations ranging <br /> from 9600 feet to 10400 feet, in very steep terrain . In order to <br /> make flat bench areas for the mine portals and other facilities , <br /> large dozers dug the shales , siltstones , sandstones and outcrop <br /> coal of the Bowie member of the Williams Fork Formation. No <br /> blasting was used to facilitate the excavation although digging was <br /> reported to be hard . <br /> Excavated material was downspoiled by the dozers in one or two <br /> locations at each portal area. Due to the steepness of the terrain , <br /> the downspoiled material was placed at angles of approximately 45' <br /> and in some places , have slope lengths of hundreds of feet . Over <br /> the years , the downspoiled slopes have not had any massive failures <br /> but gullies have formed in the material and natural revegetation <br /> has been slow. It is important to note that many of the adjacent <br /> natural slopes also have a lack of vegetation and experience <br /> significant erosion. The resulting portal areas had flat acreages <br /> of 3 to 7 acres and near vertical face-ups of up to 180 feet in <br /> height. <br /> 2. Volume of Reasonably Available Spoil <br /> The maps included in this section show the existing configuration <br /> of the portal areas and the downspoiled fill . These maps were <br /> recently developed from areal mapping at 5 ' contour intervals and <br /> are the most accurate maps made of the portal areas . <br /> The original terrain in which the portals were constructed was very <br /> steep . Grades ranged form 40' to 50` in most cases . The downspoiled <br /> material is primarily 5 to 40 feet thick , hundreds of feet wide, <br /> hundreds of feet long and has a surface angle of 45` to 50` . Simply <br /> put , it is not possible to bring this material back to the bench <br /> area for backfilling . If the material is excavated from the bottom, <br /> there is an extreme risk of fill failure as the toe of the fill is <br /> removed . It would be a safety hazard to attempt the excavation in <br /> this manner . If the fill is excavated from the top , care must also <br /> be taken to work from a firm base and keep a certain distance from <br /> the slope edge. using this method , a dozer or track-mounted <br /> excavator can reclaim the upper portion of the fill , from 20 to 40 <br />