2012-08-14_PERMIT FILE - C1996084A

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Rule 2: Permits Cross-culvert and gap exit channels will be rip-rapped down fill embankments and discharge • into riprap or straw bales to dissipate energy. Plastic sleeves (elephant trunks) or conveyor belt flumes are a design option to riprap for cross-culvert exit channels for temporary roadways not included as apost-mining facility. Discharges of runoff from haul roads within disturbed areas will be directed into sedimentation ponds. The watershed networking and configuration necessary for runoff analyses were developed from maps with a 1" = 1 000' scale and 10- foot contour intervals. Watersheds were defined by natural drainage basins above the road. Subwatersheds were defined by dendritic drainage patterns within a watershed, as well as soil types and major breaks in terrain. Flows passed by road ditch cross drains are included in upland watershed runoff quantities. Cross-culvert and ditch flow analyses were developed from maps at a scale of 1" = 400' with 10-foot contour intervals. SEDCAD+ Version 4 (Sediment, Erosion, Discharge by Computer Aided Design, developed by Ms. Pamela J. Schwab, Civil Software Design and Dr. Richard C. Warner, Agricultural Engineering Department, University of Kentucky) was used to size drainage structures. SEDCAD+ input parameters and summaries of ditch and culvert designs are presented in Exhibit 14. Map 2.05.3-3a shows drainage structures associated with the roads. The culverts listed in Exhibit 14 represent the minimum size culvert required to pass the design flow, except for requirements for culverts over 120 inches in diameter. Multiple culverts were used in those cases where a single designed culvert exceeded 120 inches in diameter. As previously mentioned, each crossing needs to be field sited and designs modified if required to • site specific conditions (width and depth of channel, etc). Alternative designs are multiple culverts or a combination of a culvert(s) and encasing concrete ford to pass the required flow. Drainage structures will be located on ephemeral or intermittent streams. An alternative design for drainage structures is to pass the 2-year, 24-hour precipitation event by culvert, and the 10- year, 24-hour precipitation event by a combination of the culvert encased in a concrete Arizona crossing. Figure 2.05.3-13 is a sketch of this option. LCC will not travel through these crossings when water is flowing. Most haul roads outside the mine areas utilize existing gas field roads. Existing and planned culvert sizes and locations are shown on Map 2.05.3-3a, Map 2.05.3-3b and Map 2.05.3-3c. The bridge over the Purgatoire River will pass a 100-year, 24-hour flood (approx. 14270 cfs - calculations in Appendix 14) given the equation's estimated percent of error. In major flood situations, it is likely the Purgatoire River will overflow its banks before overtopping the bridge. • 2.05-23 (Revised 07/28//03)