2009-10-27_PERMIT FILE - C1981041A (2)

Home Browse Search

and associated vegetation will be salvaged to a depth of 6" from the cut and fill areas where possible. The weathered sandstone and shale outcrop in this area will limit the availability of topsoil. The majority of the run-off from this road is directed to Ponds 6 and 11. See Exhibit 9B. Access Road 10 (not listed in Table 13-2) was used as a temporary ramp from the Cameo Bon'ow Area No. 2 (CBA-2) into the CRDA 1. All but 0.01 acres is within proposed disturbance boundaries of CBA-2 and Access Road 4. The small additional disturbance is a rock outcrop with no salvageable topsoil. Topsoil on previously permitted portions of the road was salvaged in accordance with permitted plans for these areas. The ramp was in place for approximately 3 weeks in June and July 1994. The former location of the road is shown on Exhibit 9A. Design calculations for road culverts and drainage ditches are provided in Appendices 13-1 and 13.2. Design calculations for two steel-pipe arches which convey runoff flow in Coal Creek beneath the access road at the Cameo No. 1 Mine are provided in Appendix 13-1. Acxording to this design review, the culverts will pass the flow from a 10-year, 24-hour precipitation event but are 13 percent undersized based on peak flow from the 20-year, 24-hour event. By installing the manufacture's inlet transitions, these culverts will pass the 20 year, 24 hour event. Three low water crossings or dip sections were installed along Coal Creek during the construction of Haul Roads 2, 3 and 4. These dip sections consist of 6 - 30 or 36" CMP culverts laid side by side and encased in concrete. A design review of the three dip sections was completed in 1982 resulting in the conclusion that the dip sections are structurally stable and environmentally sound. These structures will provide service as adequate as that obtained by disproportionately large culverts which would pass the design flow without overtopping. These findings are discussed in detail in Appendix 13.1. These structures will not carry the 20-year 24-hour design event for Coal Canyon but the concrete encasement will allow over-topping without erosion of the culverts. To avoid adding suspended solids to the drainage, coal and refuse will not be hauled across the dip sections when overtopping occurs. Appendix 13-2 includes a flow calculation across the dip section adjacent to CRDA 1. A railroad siding used for loading unit trains, and existing conveyors are shown TR-55 13-4 (Rev 02/08)