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E <br />• <br />described above. Based on our visual observations, these materials will most likely exhibit relatively low shear <br />strength due to the degree of saturation and density. <br />Based on our experience with similar slope failures and our discussion with Seneca, we believe that the most effective <br />plan for stabilizing this slope failure/landslide is to capture groundwater upslope and within the failure and then direct <br />the groundwater away from the failed materials. Based on the existing topography, which generally slopes moderately <br />down to the northwest, and the existing drainages that are situated to the north and south of the failure, we do not <br />believe that it will be feasible to regrade this area to a more stable configuration without first dewatering the existing <br />fill materials. <br />We recommend that the existing fill materials within the failure be drained by constructing a new drainage <br />channel /interceptor ditch in the fill materials. The approximate location of the ditches are provided in Pond 016 Area <br />Remediation Plan and Road Profile, Exhibit No. 20 -D.2. Sheet I of 2 and the cross sections are provided Pond 016 <br />Area Remediation Plan and Post Mine Cross Sections, Exhibit No. 20 -D.2, Sheet 2 of 2 in Appendix C. The new <br />channel /ditch (PM -2) should be similar to the section of channel /ditch that is to be constructed across the Pond 016A <br />slide and be at least 10 feet in width. The base of the channel should be properly lined with riprap or TRM. We also <br />recommend that the existing fill materials exposed in the sides of the excavations be constructed with slope <br />configurations of 3 (Horizontal) to 1 (Vertical) or flatter. <br />NWCC strongly recommends that our firm be called to the site to verify the subsurface and drainage conditions <br />exposed in the excavations, as well as to observe the installation of the drainage systems and test the backfill materials <br />placed in Pond 016A for compaction. The details and recommendations outlined in this report may require <br />reevaluation or modification based on the conditions encountered at the time of excavation/construction. <br />If you have any questions regarding the conclusions and recommendations provided in this report or the attached <br />figures or tables, or if we can bVf further service, please contact this office. <br />Sincerely <br />NWCC, <br />Brian D. <br />cc: Jay Ja <br />.lob Number: 09 -8099 NWCC, Inc. Pase 6 <br />