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data and specifications included in Appendix C. The Enkamat 7020 covered area will be non-soil ftlled • <br />except in the area of the permanent channel, which would be sod filled to promote greater stability and <br />reduce the potential for erosion. The soil filled channel will be v-shaped approximately 0.6 feet deep <br />and a minimum of 6.0 feet wide (see Figure 3, B-B' Cross Section). The entire area will be broadcast <br />seeded with the approved Seedmix #1. The existing half-round pipe will be reinstalled along the <br />drainage channel to handle flows from culvert PM-11 until Channel PM-4D has sufficient vegetation <br />established, then the half-pipe will be removed. There will be a surge pool/energy dissipater established <br />at the bottom of channel PM-4D containing riprap (Dso 6'~ to reduce the high velocity outflow (see <br />Figure 1, 2006 Neckpit Landslide Remediation Plan View). <br />The postmine channel design fox channel PM-4D is summarized as follows: <br />• Runoff was calculated fora 10-year, 24hour storm event <br />- Calculated peak runoff from a 10-yr/24hr event through culvert PM-11 is 3.7 cubic feet per <br />second (cfs) and in the lower reach of channel PM-4D is 4.2 cfs. <br />- A minimum culvert diameter calculated for PM-11 is 12 inches. <br />• Channel PM-4D has been designed as a vegetated channel with the ability to withstand runoff • <br />velocities of 20 feet per second (fps). <br />• An energy dissipater will be constructed at the outflow of postmine channel PM-4D. <br />The calculated Dso for the rock in the energy dissipater is 6 inches. <br />The SEDCAD demonstrations for culvert PM-1 ] and postmine channel PM-4D ate included in <br />Appendix B. <br />• <br />TR-55 20-B.2 12/06 <br />