2008-03-05_REVISION - M1997054 (23)

Home Browse Search

1 1 1 1 1 1 i 1 1 1 1 1 1 Table 2. Slope Stability Analysis Results Description Calculated Factor of Safety Minimum Factor of Safety Dewatered mining highwall 1.207 1.2 Case 1 - Steady state reclamation slope 1.647 1.5 Case 2 - Rapid draw down reclamation slope 1.209 1.2 Conclusions and Recommendations Case 1 - The resulting factor of safety of 1.647 is above the minimum requirement of 1.5 for the steady state case. The proposed reclamation embankment is satisfactory. Case 2 - The resulting factors of safety of 1.207 and 1.209 are above the minimum requirement of 1.2 for the rapid draw down case. The proposed mining and reclamation embankments are satisfactory. The following recommendations for monitoring of slope stability should be followed: 1. A visual inspection of the excavated highwalls should be done on a weekly basis for the first 6 months of mining. This inspection should consist of walking the existing ground and looking for any signs of stress cracks or other potential signs of slope failure. Some minor sluffing of highwalls is expected on any mine site. The intent of this inspection is to locate potential major slope failures that could potentially extend back into a structure. 2. A visual inspection should be done anytime after a major precipitation event that has saturated the ground using the same procedures. A major precipitation event would be defined as a storm that produces an intensity level reached once in 50 years on the average. 3. If a visual inspection detects signs of potential slope failure, qualified personnel should be contacted to evaluate and recommend remediation work to stabilize the area. 4. If no visible signs of slope failure are detected within the first 6 months, then the inspection period could be reduced to once per month or after every major precipitation event.