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• Relocation of underground water mains to above ground locations, thus preventing breakage of the <br />line and uncontrolled discharge of water into the slide. <br />Figure H 1 is a plan showing the location of corrective measures. Figure H4 is a cross section of the <br />landslide with the corrective measures in place. Figure H7 shows an updated construction time line for <br />both short term and long term corrective measures used to mitigate the landslide. Further detailed <br />description of the existing corrective measures can be found in the sections that follow. <br />Ongoing and additional planned correction measures for 1999 and 2000 are as follows: <br />• Rehabilitation of the F-Seam sumps near the portal entry way. These sumps, which are presently <br />unlined, collect water from mine workings, providing another source of water for the slide. Water <br />collected by the sumps escapes through fractures in the F-Seam floor and is transported to the head of <br />the slide by fractured bedrock. The plan is to install directionally drilled horizontal holes to carry this <br />water away from the head of the slide. Figure H2 shows a preliminary layout of the proposed plan. <br />• Maintenance work consisting of regrading and relining of ditches damaged by previous landslide <br />movement. <br />• Reconstruction of the main Clearwater diversion ditches above the existing portals and landslide. The <br />existing Clearwater ditch was constmcted as a combination ditch and shallow French drain, graded so <br />that water flows into a collection box within the landslide zone. The ditch and French drain are now <br />thought to act as infiltration sources into the landslide. The ditches will be reconstrcu[ed to direct <br />water away from the landslide zone. Figure H2 shows a preliminary layout of the proposed plan. <br />• Construction of deep horizontal (slope) trenches above the material storage bench. Although unrelated <br />to the main landslide, minor secondary slope instability is being experienced above the material storage <br />bench. Horizontal trenches will be installed parallel to the slope to improve drainage of the colluvial <br />mass. Figure H2 shows a preliminary layout of the proposed plan. <br />• Barr Engineering Company July 31,1999 <br />PCDOCS1206220/CAK 10 Appendix H <br />1999 Addendum to <br />1997199 Landslide Corrective Measures Report <br />