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presented in Appendix A. Soil properties a nd strength values are discussed in more <br />detail In the following sections. <br />SUBSURFACE CONDITIONS <br />Logs of the exploratory borings are presented in Appendix A. Overburden <br />soils consisted of a siltyto clayey sand with gravel. Occasicnai sandy clay seams <br />and gravelly to bouldery seams are present. The overburden soils were mostly <br />medium dense with occasional loose orvery dense layers. In borings nearthe spoil <br />fill the depth to bedrock ranged from 17 feet in the upper boring (TH-0), to 35 to 37 <br />feet at towerelevatlons. Atthewesternsedimentatlonpondarea(TH-5 through 7) <br />bedrock was not found to depths of 25 to 40 feet. The bedrock consisted primarily <br />of sandstone. A carbonaceous seam and claystone bedrock was found in boring <br />TH-4. The bedrock was medium hard to very hard. <br />. Ground waterwas found in 3 borings (TH-1 through 3) at depths of 31 to 52 <br />feet during drilling. When checked 3 to 6 days after drilling, waterwas found at <br />depths of 32 to 55 feet. Borings TH-4 through TH-7 ware dry during drilling. Three <br />days after drilling water was found at a depth of 38 feet in TH-7. <br />• SEDIMENTATION POND EMBANKMENTS <br />Weadvocateaconservativeapproachtoembankmentdesign. U. S. Bureau <br />of Reclamation guidelines for small dams, along with other references and our <br />experience, indicate small water storage embankments with 3:1 (H:V) upstream <br />slopes and 2:1 downstream slopes possess adequate stability where reasonably <br />good foundation conditions exist. Our analysis and recommendations are intended <br />to meet the requirements of CDMG Rule 4.05.9. Although detailed plans are not <br />available, we understand water impoundment heights (< 10 feet) and related <br />elevations will be selected such that embankments will not be underthe jurisdiction <br />KENNECOTT ENEROY <br />COLOWYO COAL COMPANY ~ SOUTN TAYLOR SEDIMENTATION POND <br />OTL~T JOB NO. ]6,]W h <br />• Exh. 7-20F-8 Revision Date: 1/05/07 <br />Revision No.: PR-02 <br />