Laserfiche WebLink
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 />