1987-12-01_PERMIT FILE - C1981017 (102)

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App. II-B-2 interstate highways in Colorado have been contructed in the same fashion, as it offered the most economical means for roadbuilding through steep terrain. In addition, the steep terrain which the roads traversed presented safety hazards which in themselves dictated the means of construction. Roads were cut as steeply as possible, as flatter slopes increase the excavation yardage and the final height of the cut. The cut slopes were then modified according to the geologic conditions encountered. In bedrock formations, the cut was excavated in slopes of 1/4 (H) : 1 M, or steeper. In colluvial soils as well, however, excavation was steep, frequently steeper than 45 degrees. Material from the cut was deposited as fill, although generally not compacted. Thickness of the fill depends on the topography of the ground on which it rests. On steep ground, the fill tends to roll down the hill for a considerable distance below the road. On flatter ground, the fill is thicker and in some cases the fill surface may be used as part of the roadway. a. Construction - Use of Previously Disturbed Areas. The Colorado Fuel & Iron Company developed a mining operation at the Coal Basin which operated at the turn of the century. The operation had a limited duration (1900 to 1909). Mid-Continent built the access road which connects the central complex yard with State Highway 133 along part of the railroad grade which had been constructed for the earlier operation. Later, the original mine, known as the Coal Basin mine, was reopened by Mid-Continent as our No. 5 mine, and the original rock tunnel developed by C.F.& I. is the main entry used in Mid-Continent's operation. In addition, the access road to the Sutey Refuse Pile, which has been in use since 1985, follows part of the old turn-of-the-century railroad grade. 3. Operations - Underground. Geologic factors present a formidable array of operating problems at Coal Basin. The coal beds dip steeply down, while the overlieing ground rises steeply. As a result, the mines are very deep. Depth, and rock mechanics, create stress in the areas being mined. Bumps, bounces and outbursts result, often unexpectedly, with serious consequences for safety and productivity. Dikes and faults interrupt the coal beds. The coal is gassy. The conditions encountered underground require adaptation and innovation. Mine planning is subject to change in response to the often unexpected factors of stress, gas and geology. Only because of development 2