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water tank. Road w/13% grade graded to inside at 10%, <br />.6' min depth. RSS-20--South Collection ditch on RSRDA <br />1:1 side slopes, 1% grade, 1.1' min. depth. RSS-29-- <br />South Diversion. Above first culvert, triangular ditch <br />.9'min depth, .8% grade, 2.5:1 side slopes. First <br />culvert 8" required. Diversion between culverts .3% <br />grade, 1.1' min. depth, second culvert 9" required. <br />Diversion below second culvert 5% grade, .9' min. depth. <br />CRDA2-4--East and West Collection Ditch JJ. 33% slope, <br />base width is 3', 1:1 side slopes, 11" min. depth, riprap <br />D50 of 3.7" min. 3% slope, min. depth of 17". 30" cmp <br />needed for CRDA No. 2 East Ditch. CRDA2-13--Permanent <br />Diversion Ditch. T Ditch 4' base width, 18' top width, <br />3.5' depth. <br />Volume 4 <br />Appendix 13-4 Geotechnical Investigations <br />10/24/80 Rocky Mountain Geotechnical Stability Evaluation for <br />CRDA-1. Maximum storage configuration was 2:1 side slopes <br />between 10 foot wide horizontal benches at 30 foot vertical <br />spacing, with a crest elevation of 5025'. 1.7 factor of <br />safety. <br />Roadside Mine ~1 Reject Pile Stability. Summary of Armstrong <br />Engineers 1978 report, and ARIX Corporation 1979 and 1980 <br />reports. Study conclusion was that refuse pile side slopes <br />would need to be flattened to 2.5:1 to meet required 1.5 <br />factor of safety. <br />Appendix 13-5 CRDA 2 and 3 Stability Study, Rocky Mt. <br />Geotechnical, 10/19/84. Average slopes of 2.5:1 would meet <br />1.5 factor of safety. Underdrain not required, rather, a <br />monitoring program involving the installation of several <br />piezometers along the toe of the coal refuse was recommended. <br />With proper diversion of runoff above the refuse piles and <br />proper grading of refuse piles to ensure that no ponding <br />occurs as the coal waste is placed, the coal waste piles <br />should remain unsaturated. <br />Exhibit 9A--CRDA 1 Map. Shows pile boundaries, underdrain <br />locations, soil borrow areas, certain drainage features . <br />Exhibit 6B--South Portal Sedimentation Control Plan Map. <br />Shows drainage features associated with RSRDA, including Pond <br />9, Pond 8, Lower Catch Ditch 1 (SS), Lower Catch Ditch 2 (UU), <br />South Diversion Ditch (TT) and associated culverts, various <br />berms, drop inlet drains and culverts. <br />Exhibit 9B--CRDA 1 Sediment Control Plan. Shows Pond 6, <br />Underdrain locations, bench drains, SE Collection Ditch (HH), <br />