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The following discussion is taken from Call and Nicholas, Inc. Executive Summary: <br /> As requested by the Cripple Creek& Victor Gold Mining Company (CC&V), Call& <br /> Nicholas, Inc. (CNI)performed a mine area slope design study for the mining areas associated <br /> with the Mine Life Extension 2 Project (MLE2). The purposes of the study were: (1) to <br /> determine optimum interramp slope angles and bench design parameters for the MLE2 mine <br /> areas designs, (2) to identify and analyze any potential major instability that would represent a <br /> significant cost to or interference with the mine operations, and(3)provide recommendations for <br /> slope management over the life of the project. <br /> Analytical stability analyses included: (1) bench-scale back break analysis from which <br /> the expected distribution of bench face angles (BFA) and reliability schedules were developed, <br /> (2) interramp stability which considered the stability related to faults and major structures <br /> exceeding a double bench height in length, and(3) overall wall stability associated with long <br /> release structures and weak rock mass. The back break analysis relied on cell-mapping <br /> conducted along existing mine benches in the Main Cresson and Wild Horse Extension (WHEN <br /> portion of the East Cresson mining areas. The interramp analysis was performed using mapping <br /> data collected by CC&V geologists that detailed discrete structures with trace lengths exceeding <br /> 70 feet. The overall analyses were performed using fault data, rock strength data, and drilling <br /> data to characterize the rock mass and to estimate the shear strength of the rock mass. <br /> Main Cresson and South Cresson Portion of Main Cresson Mine Area interramp <br /> Slope Angles <br /> Design sectors 1 through 4 shown on Figure 1-1 describe the MLE2 extension for the <br /> west wall of the Main Cresson and the South Cresson portion of the Main Cresson mining areas. <br /> The recommended interramp angles for these sectors range from 54 to 56 degrees and are <br /> controlled by the bench-scale analysis that determines the optimum angle required to maintain <br /> adequate catch bench widths. These recommendations assume that the benches will be <br /> excavated to a double bench height of 70 feet and that pre-split blasting will be performed using <br /> drilled depths of the full double bench for the pre-split holes. As shown, for the Main Cresson <br /> sectors, the recommended interramp slope angles are 1 to 3 degrees less than the MLE2 design. <br /> In order to achieve the MLE2 design interramp angles in the Main Cresson and South Cresson <br /> portions of the Main Cresson mining area,the excavated double bench face angles must exceed <br /> 77 degrees at least 80 percent of the time. <br /> Additionally, increasing the interramp slope angles beyond the recommended angles <br /> increases the potential for interramp failures along daylighted faults. Careful slope monitoring, <br /> including up-to-date mine area mapping and interpretation of major structures, will be required <br /> to identify zones of potential instability and to aid in the location of slope monitoring equipment <br /> including prisms, extensometers and slope radar. <br /> 24 <br />