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1 <br />1 <br />1 <br /> <br />Case 6 -Mining Conditions -Existing Utilities. There are several utilities (gas <br />lines, power poles, etc...) located adjacent to and outside of the 83rd Ave ROW. <br />A minimum 30 foot setback has been proposed for this case. <br />Case 7 -Reclaimed Condition. The proposed reclamation embankment has <br />been added to most critical mining condition cross-section (Case 1) Please see <br />exhibit F for the reclamation embankment geometry. <br />' The phreatic surface shown is considered to be the "worst" case estimate. Typically, the <br />draw down cone could extend a few hundred yards away from the highwall. This would <br />result in a "lower" phreatic line and a move stable highwall. <br />fn 0't~ <br />METHODOLOGY <br />' The embankment configuration shown in the computer analysis represents the proposed <br />reservoir embankment, which in the most critical case is a 42 foot high embankment with <br />a variable side slope. Material properties wAere obtained from typical values for the <br />t onsite soils identified in the geotechnical report. <br />Two methods were used in the computer analysis for determining safety factors; <br />t Simplified Bishop's Procedure and JanBu procedure. Both procedures search for circular <br />shear failures and automatically search for the lowest safety factor. Both methods <br />converged on nearly identical safety factors in every case. The proposed minimum safety <br />factors are based on the current standards used by the State Engineer in evaluating <br />embankment dams. <br />' SLOPE STABILITY RESULTS <br />The results of the slope stability analysis are presented in Table 2. The calculated factors <br />' of safety are within the design criteria (the State Engineers criteria for dam safety) <br />specified for this project and can be considered indicators of the embankment <br />performance under the various conditions. <br />1 Table 2. Slope Stability Analysis Results <br /> <br />1 <br /> <br />1 <br /> <br />Description Factor of safety <br />Case 1 -Mining Conditions 1.26 <br />Case 2 -Mining Conditions 1.57 <br />Case 3 -Mining Conditions 1.57 <br />Case 4 -Mining Conditions ].26 <br />Case 5 -Mining Conditions 1.26 <br />Case 6 -Mining Conditions 1.57 <br />Case 7 -Reclamation Conditions 1.77 <br />~`: ..n ~. <br />n <br /> <br />