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General Plan <br />The coal mine waste disposal area and cross sections are shown on Figure 1 <br />and Figure 2. <br />The bedrock at this site consists of the nearly flat -lying Cretaceous age Mancos <br />Shale, a transitional deep to shallow water -deposited marine shale with <br />sandstone interbeds that forms the base of the steep -sided valley in which the <br />North Fork of the Gunnison River flows. Outcrops of the Mancos Shale are <br />prominent on the south valley side. Colluvium generally covers the Mancos <br />Shale, consisting of gravity -deposited slopewash from the rocks above. <br />Outcropping about 350 -feet above the valley floor is the Rollins Sandstone, a <br />massive to bedded cemented beach sandstone about 100 -feet thick that forms <br />the basal unit of the Cretaceous age Mesaverde Formation. <br />Volume II, Map 6, Geologic Hazards shows two hazards in the subject area, <br />debris fan and sheet flow flooding and erosion. The geologic hazards are <br />considered inconsequential to the design, stability or operation of the coal mine <br />waste disposal area. Additionally, the sheet flow flooding hazard will be <br />addressed by the following water control measures section. <br />The coal mine waste bank is located in a previously irrigated field and orchard, <br />with a very small upland drainage area. Groundwater, if present in this area, <br />would consist of seepage from the Fire Mountain Canal located immediately <br />above the pile. No springs or seeps were initially detected in the founding of the <br />coal mine waste disposal area. However, later inspections noted seeps from the <br />Fire Mountain Canal had surfaced in the upper diversion ditch. More details on <br />the seep and the design of an underdrain follow beginning on page 5. <br />There has not been any underground mining under the foot print of the coal mine <br />waste bank. <br />The topography of the proposed disposal site varies from a 10 percent grade <br />near the canal to nearly level by the railroad tracks. The surficial soils at the site <br />consist mostly of granitic and some sandstone rock. Available topsoil ranges <br />averages about 2.4 feet. <br />Volume XI <br />TR -105 - 2 - 09/15 <br />