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2.0 SITE CONDITIONS <br />Site conditions in the location of the proposed waste bank were obtained from various sources <br />including: geologic maps of the area (USGS, 1976); topographic quadrangles (USGS, 1978a); <br />geologic hazard maps (USGS, 1978b); field reconnaissance conducted in late September and <br />early October 1995 by WESTEC; and borehole investigations conducted in early October, 1995 <br />by WESTEC. A plan view of the proposed waste bank is shown on Drawing 95255.01. <br />2.1 SURFACE CONDITIONS <br />Surface conditions were primarily investigated by foot in the area of the waste bank. The area <br />is covered 90 to 95 percent by low grasses, and 5 to 10 percent with scrub oak, low bushes, <br />and small pine trees. Terrain is very steep, with grades of up to 65 percent and vertical rock <br />outcrops 10 to 20 feet high. The Sanborn Creek Mine and the area of the proposed waste <br />bank are located on the south-facing side of the North Fork of the Gunnison River valley. The <br />south-facing side of the river valley is characterized by dryer surficial conditions due to longer <br />• daily sunlight exposure, and therefore mare stable hillside conditions. <br />The soil at the surface is colluvial in nature from uphill sandstone outcrops of the Bowie <br />Member of the Mesa Verde Formation. This soil is a silty sand with some gravel-sized <br />material. Existing road cuts in the West Yard yield larger, well rounded boulders indicative of <br />alluvial terrace deposits probably from the North Fork of the Gunnison River. Also present are <br />very large boulders up to 3 feet in diameter. <br />In surveying the bottom of the draw in late September and early October, it was noted that <br />no water was flowing. According to Sanborn Creek Mine personnel, water is rarely observed <br />to be flowing in the draw (Anderson, 19951, wkh the highest probability of any flow occurring <br />during high-intensity rainfall events, and during spring runoff conditions. No springs were <br />noted within the draw during the WESTEC field investigations, and according to the mine <br />personnel, springs have not been observed in the recent past (Anderson, 1995). <br />Rock outcrops near the toe of the proposed coal mine waste bank were mapped at the time <br />of the borehole investigation in early October, 1995. The outcrops were probably exposed <br />• during cuts made for the Denver and Rio Grande Western Railroad right-of-way at the toe of <br />95255/1424.RPT Coal Mine Waste Benk Deeipn for the Sanborn Creek Mins <br />October 1998 WESTEC, Inc. 2 <br />