2001-12-11_PERMIT FILE - C1981019 (6)

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0 • July 17, 1995 Colowyo Coal Company L.P. 5731 State Highway 13 Meeker, Colorado 81641 Attention: Mr. Juan Garcia Subject: Geotechnical Assessment Proposed East Taylor Creek Sedimentation Pond Colowyo Coal Mine Moffat County, Colorado Job No. 23,085 Gentlemen: At your request, we have performed a geotechnical assessment of the proposed East Taylor Creek Sedimentation Pond. The purpose of our assessment was to review available information, Colowyo's sedimentation pond design, and develop general recommendations for your use in design of the pond, Proposed Construction The approximate location of the proposed pond is shown on Fig. 1. Current plans are to excavate soils from the southern portion of the pond and construct an embankment across the valley at the north end. The embankment will be on the order of 15 to 20 feet in height. A gated outlet structure and emergency spillway over the embankment will be provided, and a light use road along one side of the pond is also planned. Site Conditions The site is located west of the west pit. The future west pit excavation will cross East Taylor Creek at the approximate location shown on Fig. 1. We understand Taylor Creek flows most of the year in this area, the East Taylor Creek drainage flows intermittently arid was not flowing at the time of our site visit in May of 1995. Based upon the topographic map, the east and west slopes of the valley are on the order of 2:1 (horizontal:vertical) overall, with occasional steeper areas approaching 1.7:1. The east slope is sparsely vegetated with very thin soil cover, most of the slope is exposed, weathered bedrock. The west slope is covered with grasses and scrub oak, with occasional layers of weathered sandstone exposed. • Soil cover maps (Soils South Sheet, by R. G. Trumbly, Jr., for Colowyo Coal CTL/THOMPSON, INC. CONSULTING ENGINEERS 1971 WEST 12TH AVENUE • DENVER, COLORAD080204 ~ (303) 825-0777