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Pitdt Reclamation Project -Sediment Control Embankment November, 2002 <br />evaluation. <br />Figure 5 shows a profile of the embankment and piezometer elevations relative to the crest of <br />the embankment and the water level readings at the time of installation. The approximate depth of the <br />gravelly layer intercepted in P-6 and P-7 is also shown in Figure 5. Borehole logs and piezometer <br />completion data are presented in Appendix B. In addition, a summary of piezometer readings is <br />included in the appendix, <br />4.0 STABILITY ANALYSIS <br />4.1 General <br />Stability analyses were run on the embankment to evaluate safety based on [he collected field <br />data and piezometer readings. The purpose of the analyses was to determine the safety of the <br />embankment under current conditions assuming no remedial work to control the seepage. The analyses <br />were extended to determine acceptable operating levels of the pond since remedial work to control the <br />seepage through the embankment would not be completed until after spring runoff in 2001. Only the <br />downstream slope of the embankment was considered in this evaluation as all other azeas appeazed <br />stable and showed no signs of distress. <br />The stability evaluation consisted of several slope analyses completed using the computer <br />program XSTABL developed at University of Idaho. This program incorporates the PCSTABL slope <br />stability computer program developed at Purdue University. The slope conditions considered in this <br />evaluation incorporated the updated slope survey data, phreatic surfaces through the embankment <br />modeled from the piezometer data, and soil strength pazameters presented in the as-built slope stability <br />analysis conducted in 1981 by Bingham Engineering of Salt Lake City, Utah and revised values <br />estimated from the October 2000 drilling data. A summary of the slope conditions and the results of the <br />stability analyses are presented in the following sections. <br />The cases considered in this evaluation included the full. height of the slope and the mid section <br />in the area of the seep. Strength parameters and phreatic surface locations were varied in the analyses <br />as explained below. Printouts of selected analyses are presented in Appendix C. <br />The Homestake Mining Company -iS- The Clasgow Engineering Graup,/nc. <br />