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F~ <br />• High groundwater and pore water pressures in the slope affect <br />the shearing resistance that can be developed. Methods to lower <br />the zone of subsurface water and intercept surface water to prevent <br />infiltration, and to reduce seepage forces, such as conventional <br />interceptor and collector drains are preferred for both their <br />effectiveness and economy. The installation of horizontal weep <br />holes was given consideration as a possible fix for the unstable <br />area. Some holes could be drilled from the mine access road into <br />the formation immediately above the slide area without any <br />additional disturbance but, due to the cost and close proximity to <br />the french drain these holes where eliminated from consideration. <br />The installation of horizontal weep holes further down the slide <br />area were rejected based upon the additional disturbance required <br />for drilling the slide, the economic cost to drill and place the <br />weep holes, and the apparent effectiveness of the french drain in <br />intercepting the near surface groundwater flow. <br />Because no highways or public buildings are planned at the <br />• site and probably never will, cost is an appropriate consideration <br />for the remediation method or methods chosen for the site. Any or <br />all of the more expensive remediation methods described above could <br />theoretically increase the factor of safety for the slide and <br />completely stabilize the area. The safety factor realized from the <br />methods evaluated must be weighed with the capital expenditures <br />required to implement the corrective measure chosen. Due to the <br />minimal presence of hazards to the publics' health and safety at <br />this site, the high cost to implement procedures that realize the <br />maximum factory of safety is not considered necessary. The <br />following repair plan may produce a slightly lower factor of safety <br />than a repair plan that utilizes more expensive remediation <br />methods. However, the lower factor of safety is acceptable <br />considering, as explained above, the minimal presence of hazard to <br />the public health and safety at this site. <br />• <br />21-9 <br />