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i <br />'~ <br />r~ <br /> <br />IAYoodvvard-Clyde <br />Censultar~ts <br />on Tailing Dam Stability" report dated January 26,1990. A sand beach width of 700 feet <br />was assumed for the embank®ent below Elevation 8708, and 400 feet above this <br />elevation. The internal tailing embanlmlent geometry was assumed to be the same at <br />each of the five study sections. The natural ground profile beneath the tailing dam was <br />established at each study section using the original ground topography as <.,hown on the <br />Lower Tailing Pond Dam Subdrain Piping Details Drawing No. 5-2-301 prepazed by <br />W.W. Wheeler & Associates, Inc. dated March 1971. <br />The cross section geometry for the raised embanlonent was constructed by raising the <br />crest of the existing embankment geometry to Elevation 8900 at a 4:1 slope. The sand <br />beach width for the raised section was assumed to be 400 feet, same as for the upper <br />section of the existing embankment. <br />3.2.2 Material Properties <br />Material properties input for the slope stability analyses include effective stress strength <br />pazameters and total unit weights. The material properties used for the analyses <br />presented in this study aze based on previous studies including the tailing grind study <br />cited above. T'he material properties used aze the same as those used for previous slope <br />stability analyses performed by WCC. <br />3.23 Phreatic Levels <br />I "' Pore water pressures for the slope stability analyses performed in this study aze <br />~i estimated based on the assumed location of the phreatic surface with hydrostatic <br />I9 conditions assumed below the phreatic surface. Evaluation of the stability of the existing <br />!~ height embankment utilized a phreatic surface that corresponds to the February 1992 <br />i piezometer readings as provided by AMAX. Upstream of the slope the phreatic surface <br />is assumed to extend to the upper tailing surface at the tailing sand%tailing slimes <br />'~~ interface and is assumed to be at the surface upstream within the tailing slimes. <br />Downstream of the slope the phreatic surface is assumed to be at the toe of the <br />embankment and then at the ground surface downstream of the slope. For the threshold <br />level analyses of the existing height embankment and the planned raised embankment, <br />the location of the phreatic surface upstream and downstream of the slope Was held the <br />us9veu adm-»nrt 3-2 <br />