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<br /> <br />5. The safety factor calculated for a rapid drawdown condition is 1.90 which <br />exceeds the minimum criteria of 1.2. This cases assumes that the reservoir is <br />evacuated in a short enough time period that pore water pressures in the <br />embankment are not reduced. <br />6. These safety factors are based on obtaining a saturated cohesion of 200 psf for the <br />soil in the embankment. Based on results of direct shear tests on similar soils a <br />700 psf cohesion value was obtained. The 200 psf value was selected as a <br />conservative value for the purposes of analysis. <br />7. The safety factors are based on an assumed value for the strength of the bedrock <br />on the site. The strength of the bedrock has no impact on the stability of the <br />mining highwalls. A failure surface will not initiate or propagate through the <br />bedrock material A conservative c value of 300 psf and a friction angel of 45 <br />degrees was selected to represent the strength of the bedrock <br />The stability analysis and resulting factors of safety are based on assumed values for soil <br />properties for this site. The values selected are representative of soils in this azea and are <br />considered to be conservative. <br />The following recommendations for monitoring of slope stability should be followed: <br />1. A visual inspection of the excavated highwalls should be done on a weekly basis <br />- for the first b months of mining. This inspection should consist of walking the <br />existing ground and looking for any signs of stress cracks or other potential signs <br />of slope failure. Some minor Bluffing of highwalls is expected on any mine site. <br />` The intent of this inspection is to locate potential major slope failures that could <br />potentially extend back into a structure. <br />2. A visual inspection should be done anytime after a major precipitation event that <br />has saturated the ground using the same procedures. A major precipitation event <br />would be defined as a storm that produces an intensity level reached once in 50 <br />years on the average. <br />3. If a visual inspection detects signs of a potential slope failure, qualified personnel <br />should be contacted to evaluate an recommend remediation work to stabilize the <br />area. <br />4. If no visible signs of slope failure are detected within the first b months, then the <br />inspection period could be reduced to once per month or after every major <br />precipitation event. <br />4 <br />