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<br /> <br />5.0 ENGINEERING STABILITY ANALYSIS <br />The recommended slope angles and configurations for the final reclamation slopes in <br />rock are based on five different analyses that provided a comparison of the critical <br />factors controlling the final slope configurations. These analyses included rock mass <br />durability, kinematic stability, limit equilibrium block stability, global stability, and rockfall. <br />The rock mass durability generally controls the slope configuration in weaker <br />sedimentary rocks. The kinematic analysis controls the slope configuration in hard <br />durable rock masses, where rock blocks formed by the intersection of discontinuities <br />can potentially fail out of the cut slopes. The limit equilibrium block stability analysis is <br />used to establish a factor of safety for blocks identified in the kinematic analysis. The <br />global stability analysis can control the slope configuration where there is a potential for <br />failure surfaces that cut through weaker or more weathered and fractured rock or along <br />a prevalent structural feature. Finally, a rockfall analysis is used to establish the <br />rockfall trajectories and required catchment basins for a given slope configuration. The <br />results of the different analyses are evaluated to develop the final recommended slope <br />angles and configurations. <br /> <br />The recommended slope angles and configurations for the final reclamation slopes in fill <br />materials are based on a conventional limit-equilibrium, method of slices, analysis that <br />utilizes the fill slope geometry, unit weight and shear strength properties to calculate a <br />factor of safety for anticipated loading conditions. Factors of safety were calculated for <br />three anticipated loading conditions including long term normal dry conditions, extreme <br />rainfall conditions that saturate the base of the fill, and earthquake loading conditions. <br />The final slope angles and configurations are based on a parametric analysis that varies <br />bench height, bench slope angle, bench width and overall slope height to obtain the <br />recommended slope configuration. <br /> <br />6.0 ROCK SLOPE ANGLES AND CONFIGURATIONS <br />The existing highwall and rock slopes can be left in place with no modifications where <br />they will be completely covered by stable fill slopes. Where the highwall and rock <br />slopes will remain exposed, the final reclamation slopes can have the following <br />configuration (See Figures 7.1 through 7.5 of Attachment A): <br /> <br />• Dacite left at existing slope angle with loose rock scaled from the face of the <br />dacite. <br />86995/DEN8R017 Page 3 of 5 February 2008 <br />Copyright 2008 Kleinfelder West, Inc.