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accordance with permitted plans for these areas. The ramp was in place for <br />• approximately 3 weeks in June and July 1994. The former location of the road <br />is shown on Exhibit 9A. <br />Design calculations for road culverts and drainage ditches are provided in <br />Appendices 13-1 and 13.2. Design calculations for two steel-pipe arches which <br />convey runoff flow in Coal Creek beneath the access road at the Cameo No. 1 <br />Mine are provided in Appendix 13-1. According to this design review, the <br />culverts will pass the flow from a 10-year, 24-hour precipitation event but are 13 <br />percent undersized based on peak flow from the 20-year, 24-hour event. By <br />installing the manufacture's inlet transitions, these culverts will pass the 20 <br />year, 24 hour event. <br />Three low water crossings or dip sections were installed along Coal Creek <br />during the construction of Haul Roads 2, 3 and 4. These dip sections consist of <br />• 6 - 30 or 36" CMP culverts laid side by side and encased in concrete. A design <br />review of the three dip sections was completed in 1982 resulting in the <br />conclusion that the dip sections are structurally stable and environmentally <br />sound. These structures will provide service as adequate as that obtained by <br />disproportionately large culverts which would pass the design flow without <br />overtopping. These findings are discussed in detail in Appendix 13.1. These <br />structures will not carry the 20-year 24-hour design event for Coal Canyon but <br />the concrete encasement will allow over-topping without erosion of the culverts. <br />To avoid adding suspended solids to the drainage, coal and refuse will not be <br />hauled across the dip sections when overtopping occurs. Appendix 13-2 <br />includes a flow calculation across the dip sections in the event that the culverts <br />plug. <br />A railroad siding used for loading unit trains, and existing conveyors are shown <br />13-4 (Rev.3/1/96) <br />