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I <br />I <br />I <br />I <br />I <br />I <br />is <br />I <br />I <br />I <br />Y -L <br />4.0 EMBANKMENT ANALYSIS AND EVALUATION <br />Analysis and evaluation of the Bulldog Mountain Operation lower tailings <br />dam has been conducted with regard to slope stability and general integ— <br />rity of the structure. Slope stability was analyzed for three cases, <br />(a) existing dam height and pool elevation, (b) existing dam height and <br />maximum pool elevation (E1. 8955), and (c) raised dam height (crest E1. <br />8975). Factors of safety for each of these cases under static and <br />pseudostatic earthquake conditions were calculated using a computer <br />slope stability program. The slope stability analytical model was <br />developed from the geologic and hydrologic model and is discussed in <br />Chapter 3.0. <br />The general integrity of the dam including the potential for piping type <br />erosion was analyzed using the pressures, flow quantities, and other <br />hydrologic/hydraulic observations. Various mechanisms for piping were <br />considered and evaluated based on the conditions modeled in the dam. <br />The following sections present the methodology used in these analyses <br />and the results. <br />4.1 SLOPE STABILITY ANALYSIS <br />Slope stability of the lower tailings dam was assessed using a limiting <br />-equilibrium type computer analysis and an analytical model developed <br />from the geologic and hydrologic dam model shown in Figure 8 and <br />discussed in Chapter 3. <br />The analytical model is also shown in Figure 8. The model consists of <br />five materials as follows: <br />o Material Type 5 — Bedrock <br />o <br />Material <br />Type <br />1 — Compacted Dam Fill <br />o <br />Material <br />Type <br />2 — Chimney/Blanket Drain <br />o <br />Material <br />Type <br />3 — Alluvial Soil <br />o <br />Material <br />Type <br />4 — Weathered and Fractured Bedrock <br />o Material Type 5 — Bedrock <br />