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r~ <br />Mountain Coal Company <br />West Elk Mine <br />Exhibit ?7 <br />Characteristics of West Elk Mine Soil Mapping Units <br />A. Ustic Torriorthents (Regosols of semi-arid regions). <br />t. Fine-loamy, mixed. (calcareous), mesic family. <br />(Thedalund Seriesj <br />(Kim Series) <br />(Shavano Series) <br />2. Fine-loamy, mixed, (calcareous), frigid famil}~. <br />(Patent Seriesl <br />B. Ustollic Cambonhids (Regosols of Semi-arid regions). <br />1. Fine-loamy, mixed, mesic. <br />(Zigivied Series) <br />C. Borollic Camborthids (Regosols of cold dry regions). <br />1. Fine-loamy, mixed. <br />(Chapperton Series) <br />Extent and Major Areas of Occurrence -Mapping unit number 4 occurs in limited <br />acreage in the study area. Largest areas are located on the valley filling sideslopes east <br />• and north of Minnesota Creek and its eastern fork in the southwestern part of the study <br />area. <br />Characteristic TopographX -These soils occur on gently to moderately sloping valley <br />filling sideslopes and coalescing alluvial fans below steep escarpment-like areas bordering <br />the major stream valleys. They have been dissected by numerous steep walled drainage <br />channels that formed more or less at right angles to the major channel of the North Fork <br />of the Gunnison River. <br />These areas are young land surfaces that are still geologically active. Slopes range from <br />about 5 percent to 40 percent with the steeper sloping areas normally occurring along the <br />edges of the dissecting streams. <br />Physical Properties -The soils of this unit are young and lack well developed natural <br />soil structure. They typically have moderate grades of soil structure, making <br />management a requisite in an operation requiring good permeability and aeration after <br />disturbance. They are subject to packing if traversed by heavy machinery and <br />itteversible puddling if handled when too wet. <br />The soils of this unit have moderate shrink/swell potentials with coefficients of linear <br />extensibility ranging from about 0.02 to 0.05 in most areas, and total potential <br />extensibility within a 40 inch thickness of about 0.4 to 2.0 inches. when ~~et they are <br />• moderately slippery• and sticky. Disturbed deposits from these soils can generally be <br />worked down into good erosion-resistant seedbeds ~yith conventional machinery and <br />practices. <br />Exhibit '7-3 <br />