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testing. A remolded sample (93 percent ASTM D 698) showed friction of 45 degrees <br />cohesion of 330 psf. <br />The strength values from these various sources are summarized on Fig. 2. <br />For this analysis we used the bi-linear strength envelope (Curve 8) shown on Fig. 2. <br />This represents a lower bound of the total and effective strength results from the <br />CU testing pertormed for this site (Curves 5 and 6, Fig. 2-. The overburden soils <br />vary in gradational characteristics and are primarily granular, have lower plasticity <br />fines, and are medium dense. This soil type would be expected to have a significant <br />frictional strength component. At higher normal stresses the implied cohesion of <br />the envelope is considered reasonable. This strength value was used for both the <br />foundation soils and the compacted embankment. <br />Stability Evaluation <br />We recommend an upstream slope of 3:1 (H:V) and a downstream slope of 2:1. <br />• Wealsorecommendakeywaytrenchatthebaseoftheembankmentwithaminimum <br />,width of 8 feet and a minimum depth of 6 feet. The keyway should be continuous <br />below the embankment, extending into and up the abutments. The upstream face <br />and spillway should be protected from erosion as required. A conceptual detail of <br />the recommended embankment section is shown on Fig. 3. <br />We analyzed the stability of this model using SLOPEMI and SEEPAN software <br />(References 4 and 5). The soil properties, analysis cases and output are presented <br />in Appendix B. We utilized a bi-linearstrength envelope as shown on Figure 2 and <br />discussed above. <br />A maximum 10-foot height of water impoundment was used, SEEP/W <br />calculated the phreatic surtace and pore pressures based upon the permeability <br />estimates shown on Table B-I. <br />KENNELOTT ENERGY <br />GOLOWYO COAL COMPANY- sOUTN TAYLOR SEDIMENTATION POND <br />CTL~T JOE ND. 9E~86/ 9 <br />Exh. 7-20F-10 Revision Date: 1/05/07 <br />Revision No.: PR-02 <br />