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Case West — South Property Line (WEST). The mining operation is adjacent to <br />private property with several permanent structures near west property line of the <br />site. The mining depth was assumed to be 52.5 feet in this area based on bore <br />log information in the geotechnical reports. The proposed mining setback was set <br />50 feet from the property line <br />The cross - sections located in Appendix B show the estimated phreatic surface <br />associated with each case as well as the geometry used in the mining. <br />METHODOLOGY <br />The mining embankment configuration shown in the computer analysis represents the <br />estimated conditions for this site. If mining conditions differ from the estimated <br />conditions, the slope stability will need to be re- evaluated on a case by case basis. The <br />Bishop Method was used in the computer analysis for determining safety factors. The <br />procedure searches for circular shear failures and automatically searches for the lowest <br />safety factor. 2,000 separate failure surfaces were analyzed for each case. The required <br />minimum safety factors are based on the current standards used by the Colorado State <br />Engineer's Office (SEO) in evaluating embankment dams, and industry accepted <br />standards for the evaluation of temporary structures during construction. <br />SLOPE STABILITY RESULTS <br />The SEO requires minimum safety factors of 1.3 for static condition analyses and 1.0 for <br />pseudo- static (earthquake loading) condition analyses for Class I (high hazard) <br />embankment dams. This design criteria was used to establish the desired minimum <br />safety factors for this project and should be considered as highly conservative for <br />evaluating alluvial mining slopes. The calculated factors of safety are within the design <br />criteria specified for this project and can be considered indicators of the mining slope <br />performance under the various conditions. The results of the static condition and <br />pseudo- static condition slope stability analyses are presented in Table 2 and Table 3. <br />Table 2 - Static Condition Slope Stability Analysis Results <br />Description <br />Calculated <br />Factor <br />Of Safety <br />Required Minimum <br />Factor Of Safety <br />Case North — North Property Line <br />1.74 <br />1.30 <br />Case South — Property Line <br />2.08 <br />1.30 <br />Case East — Existing Balsam Avenue ROW <br />1.58 <br />1.30 <br />Case West — West Property Line <br />1.83 <br />1.30 <br />. Loloff Construction, Inc. - Loloff Pit <br />J&T Consulting, Inc. Slope Stability Analysis <br />3 <br />Page 3 <br />