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4.1.4 Sediment Pond Access Road <br />i A sediment pond access road will be constructed prior to sediment pond construction and <br />located and topographically below the cemetery/haul road, beginning at EI. 6,080 ft. The haul <br />road will be constructed at an average grade of 1 percent before descending into the sediment <br />pond. The plan and profile of this road is shown on Drawing 95255-05 and details on <br />Drawing 95255-03. The road will be approximately 20 feet wide, with a small safety berm <br />on the outside. Runoff intercepted by this sediment pond access road will be minimal, so only <br />small, unlined ditch should be placed on the inside of the road. Small quantities of runoff and <br />associated sediment that may accumulate cannot be routed to the sediment pond due to <br />topographic restrictions. A small area exemption from the sediment control requirements is <br />needed from the Division of Minerals and Geology, and best management practices (BMP) <br />should be used; such as silt fences and revegetation. Proper maintenance should be <br />performed regularly to remove any collected sediment. The sediment pond access road should <br />be surtaced, maintained and reclaimed similarly to the haul road. <br />4.1.5 Runoff Control Ditches <br />• Runoff control ditches will be located around the coal mine waste bank to divert runoff within <br />and above the disturbed area produced by a 100-year, 24-hour storm to the sediment pond <br />with a minimum of 0.3 feet of dry freeboard. This stone frequency corresponds to 2.8 inches <br />(J.E. Stover & Associates, 1995). This storm was modeled as described in Section 4.2. <br />Worksheets used in calculating flow depths and velocities are attached in Appendix C. Riprap <br />and filter material placed in these ditches for erosion protection were designed using <br />information in the Surface Mining Water Diversion Design Manual by the Office of Surface <br />Mining (OSM, 1982). In most cases, the ditch will have to be over-excavated to <br />accommodate the riprap and filter thickness requirements to achieve the proper channel <br />geometry. <br />Locations of the runoff control ditches are shown on Drawing 95255-01. Side ditches <br />primarily run along the contact between the coal mine waste bank and the natural ground. <br />These ditches should be a minimum of 1-foot deep, whh 2:1 side slopes, and will require slope <br />protection in the form of riprap. Riprap with a protective filter layer below should follow <br />requirements shown on Drawing 95255-03 for the side ditches. The 23-inch maximum riprap <br />size recommended for these side ditches is large, compared to ditch size and flow depth. This <br />96265/1424.RPT Coal Mine Weate 9enk Dseipn for the Sanborn Creak Mine <br />October 1898 WESTEC, Inc. tD <br />