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11 <br />large slope failure could potentially occur at any time. For comparison, we estimate <br />that this second slide could potentially expand the failure area by up to 8 acres in area <br />and add about 1.3 million cubic yards in volume. <br />Large slope failures have a tendency of continued movement over a period of several <br />years unless remedial measures are implemented. Typically, periods of inactivity may <br />be followed by renewed slope movement, most commonly triggered by periods of <br />above-normal precipitation. Remedial measures are usually unsuccessful unless they <br />are based on a thorough monitoring, subsurface exploration-and engineering analysis of <br />the slope failure. -' <br />Appropriate mitigation measures can only be speculated upon at the time of this report; <br />however, due to the large size and geometry of this slope failure and the narrow width <br />of the pit, it seems unlikely that a stabilization scheme could be implemented that <br />would allow for the safe continuation of mining in the southern portion of the pit and <br />lower benches. Cr_ <br />RECOMMENDATIONS <br />The following recommendations are presented to help ensure the safety of personnel <br />and to develop a plan for eventual remediation of the slope failure. <br />1. The pit should remain closed to entry by personnel until sufficient information is <br />obtained to determine trends of ground movement. However, activities directly <br />related to ongoing assessment of the pit stability, such as installation of monitoring <br />equipment will entail unavoidable entry into the pit. Continuous movement <br />monitoring of pit slope and highwalls will be required whenever personnel are on <br />the slope or in the pit for these activities. The operator should develop a specific <br />monitoring plan for all monitoring and subsurface exploration activities in the pit. <br />2. A thorough analysis of the unstable pit slopes and the development of any <br />remedial measures will require extensive engineering and geologic studies which <br />should be developed by a qualified geotechnical engineer or engineering geelegis <br />As a minimum, the scope of any proposed study should include the items listed by <br />Yenter, as described in the section "Site Briefing - December 4" above. <br />3. Re-opening the existing haul road to the pit floor would require excavating the toe <br />materials of the slide and could be extremely hazardous to personnel involved. <br />Therefore, any plan to remove the equipment currently in the pit will require that <br />it be removed to the north, using a ramp of fill to the bench to the north. No <br />excavation in the pit area should be performed unless it is part of a specific <br />engineered remediation of the pit slope.