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SCC typically constructs ditches on the inside of roadway cuts for drainage. Atypical V-ditch section <br />• would be a minimum of two feet deep with side slopes 2:1 or flatter. As most road cuts are into <br />resistant bedrock-type material, ditches normally do not require lining. Culverts wiN be designed and <br />installed to minimize the runoff volume conveyed in each ditch. Culverts and ditches will typically be <br />designed using SEDCAD+ to predict the peak runoff and Manning's equation to determine the peak <br />velocity and flow depth Isee Attachment 13-11• <br />If the ditch is not stable, then a larger ditch section will be used and/or adequately line the ditch in <br />order to comply with applicable regulations. <br />Drainage from access roads within the areas disturbed by mining and reclamation activities (see <br />Exhibits 13-2 and 13-31 will be constructed to meet the requirements of 4.05.2 and such access roads <br />will at a minimum be constructed and maintained to minimize erosion of the. disturbed area. Erosion <br />control measures to be used singly or in combination include but are not limited to: <br />a. Stabilizing alt exposed surface areas to promote- a reduction in the rate and volume of <br />runoff; <br />b. Using straw dikes, riprap, check dams, berms, geotextile materials, mulches, vegetation <br />sediment filters, contour furrows ar other measures that reduce overland flow velocity, <br />• reduce runoff volume, or trap sediment; or <br />c. Such other measures to minimize erosion resultant siltation and disturbance to the prevailing <br />hydrological balance. <br />Surfacing. See Exhibit 13-10 for typical detail. <br />Culverts. Each access road will be designed, constructed, and maintained to have adequate drainage <br />using ditches and culverts to safely convey the peak runoff from a 10-year, 24-hour precipitation event <br />to sediment ponds before being released from the permitted area Isee Exhibit 13-10~for typical details <br />of drainage structuresl. <br />Culverts will be installed to avoid plugging or collapse and to avoid erosion at the inlets and outlets. <br />Riprap will be installed as necessary to reduce the exit velocity. The minimum width will be the width <br />of the natural downstream channel. The riprap will be sized in the field 6y SCC's project engineer <br />based on the "as-built" slope of the culvert and final configuration of the exit channel slope area. The <br />sizing shall be based on the Federal Highway Administration's HEC No. 11 "Use of Riprap for Bank <br />Protection" or other standard methods. All culverts will have a minimum cover of i 2 inches. Culverts <br />and <br />33 Revised 4/24/91 <br />