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<br /> <br /> <br />West Elk Mine - Mine Water Control Plan <br />3.0 SEDCAD INPUT PARAMETERS FOR SUBWATERSHEDS <br />3.1 Subwatershed Boundary <br />Subwatershed boundaries were digitized in AutoCAD using the site contour maps. Map 54 <br />depicts the main mine site, and Map 54B depicts facilities in Sylvester Gulch. <br />3.2 Soil Type & Land Cover <br />The soil type-land cover complex determines a number of SEDCAD input parameters relating to <br />both hydrology and erosion. Custom soil maps and reports were obtained for the main mine <br />site and Sylvester Gulch from http://websoilsurvey.nres.usda.gov/, USDA's online GIS-based <br />soils data source. Soil boundaries were digitized in AutoCAD from the map images. The <br />following soil types were mapped within the site boundaries: <br />Soil I.D. Soil Name <br />2 Absarokee-Work loams <br />13 Beenom-Absarokee association <br />17 Breece loam <br />39 Fughes loam <br />74 Torriorthents-Haplarg ids <br />75 To rriorthents- Rock outcrop <br />85 Water / Marsh <br />124 Coberly-Falcon, dry complex <br />130 Cryochrepts-Cryoborolls-Rubble land complex <br />153 Haploborolls-Ustochrepts-Rock outcrop complex <br />157 Herm-Fughes complex <br />158 Herm-Fughes-Kolob family complex <br />188 Tate rheap-Papaspila complex, 5 to 40 percent slopes <br />189 Tate rheap-Papaspila complex, 40 to 65 percent slopes <br />192 Torriorthents, cool-rock outcrop <br />Land cover was determined from field inspections and viewing the aerial photos over which the <br />custom soils maps are drawn. Areas erroneously shown as Water / Marsh were revised to <br />reflect the adjacent soil map unit. The following land cover types were present on the site: <br />• Revegetated areas include reclaimed refuse piles. They are differentiated from pasture <br />to reflect soil compaction by heavy equipment. <br />• Oak land cover reflects undisturbed wooded areas, chiefly containing scrub oak, aspen, <br />and mountain brush species. <br />refuse piles, and bare earth. <br />• Impermeable land cover includes open water and HDPE pond liner. <br />• Paved includes areas covered in asphalt, concrete, or building rooftops. <br />• Pasture includes undisturbed grassy areas and reclaimed soil stockpiles <br />• Coal product was developed to represent areas covered by coal stockpiles. <br />• Disturbed represented bare or gravel-covered materials storage benches unreclaimed <br />Mountain Coal <br />Coal product, disturbed, impermeable, paved, and revegetated areas were assigned soil <br />parameters selected to reflect their disturbed condition. Oak and pasture areas were assigned <br />soil parameters based on the actual soil type. <br />Tetra Tech <br />October 2008 <br />3