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~, " Colowyo Cool Company <br />Tipton and Kalmbach, Inc., Engineers <br />STABILITY OF SPOIL FILL IN STREETER GULCH <br />July 1978 <br />The Colowyo Cool Company's open-pit coal mine is situated approximately 22 <br />miles southwest of the town of Craig in Moffat County, Colorado, on Federal Coal <br />Lease D034365. Overburden removed in excavating the initial pit near the northern <br />boundary of the Lease is being placed in Streeter Gulch, a natural canyon lying just <br />to the north of the area to be mined. The natural ground at the head of the canyon in <br />which the spoil is being placed lies at about 7,000 foot elevation and descends through <br />a relatively narrow valley down to elevation 6600 in a distance of approximately 6,000 <br />feet where it joins the valley of Good Spring Creek. When the spoil fill reaches its <br />final configuration, approximately 16(O) million cubic yards of material will have been <br />placed in Streeter Gulch, transforming the topography of the canyon to the configuration <br />depicted on the section shown in Figure 1. <br />Placement of fill in Streeter Gulch commenced in January 1977; and as of this <br />date (July 1, 1978), approximately 8,000,000 bank cubic yards have been placed. <br />Overburden excavated by shovel and front end loader is hauled in dump trucks to its <br />c <br />point of disposal in the canyon and dumped over the edge of the outer slope of each <br />lift. In this operation the overburden, consisting of a mixture of sub-soil and fragments <br />of shale and sandstone, assumes an angle of repose of approximately 38°. In the lower <br />part of the canyon, the spoil fill has been carried to approximately 6800 foot elevation <br />and material is currently being placed in the next lift up to about 6900 foot elevation. <br />Subsequent lifts will only be of full height on the south side of the canyon and descend <br />on a 3:1 slope to 6900 foot elevation on the north side of the draw so as to provide <br />natural drainage to the relocated channel of Streeter Gulch olong the north abutment <br />of the canyon. After the required volume of material in each lift has been placed by <br />end dumping, the outer portion of the fill is reworked by bulldozers to reduce the <br />Outside of areas to be mined <br />