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angle of friction of 33° and a density of 82 pounds per cubic foot. The reclamation <br />stability cross section at Station 51+00 was reevaluated based on the coal placed in the <br />backfill and the strength parameters of the coal. The slope stability analysis was <br />performed using SB-Slope by Geosystem software. The slope stability analysis <br />considered numerous possible failure surface iterations to help identify the potential <br />theoretical slope stability. The stability analysis indicated a factor of safety of 1.78. <br />3.3.4 Reclaimed Ephemeral Channels <br />Lower Road Channels <br />The reclamation of the mine site and road included establishing stable <br />ephemeral channels across the reclaimed area. Two major channels cross the lower <br />portion of mine road, Munger Creek near the topsoil stockpile and the channel draining <br />the major canyon south of the road near where the waste rock disposal area was <br />proposed. Both channels are now diverted under the road with culverts. When the <br />culverts are removed, dry fords will replace the culverts. The reclaimed configuration of <br />each is shown on Figure 2.2-7C. <br />f <br />~_ Calculations for the size of the reclaimed channels on the lower road are <br />contained on Table 3.9-5. These calculations are based upon previous surface water <br />hydrology studies for the two lower channels. The calculations are shown in Appendix <br />M(v) for the 100 year event at the 72" culvert and Appendix M(i) for the 10 year event at <br />the 42" culvert. Pages 3 and 4 of Table 3.9-5 show the drainage area, flow calculations <br />and channel design for the 18" culvert near the topsoil stockpile. <br />Although the channels have been designed for non erosive water velocities, <br />riprap keys will be installed in the channels to protect the fords. Gravel will be placed <br />on the road surface to minimize rutting of the channel with wheeled traffic and the <br />ensuing erosion. Riprap keys will be installed at the upstream and downstream edges <br />of the ford. The riprap keys will be a two foot wide by two foot deep slot dug into the <br />channel bottom on both sides of the reconstructed channel. The keys will be lined with <br />geotextile fabric and filled with one foot top size riprap. These rip rap keys will ensure <br />that the fords will not be washed out during high flow. The gravel will be reclaimed from <br />the existing road where the road base is excavated in the process of building the ford. <br />TR-23 3-14 12/07 <br />