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Peabody typically constructs ditches on the inside of roadway tuts for drainage. A <br />typice( V-ditch section would be a minimum of two feet deep with side slopes 2:1 or <br />. flatter. As most road cuts are into resistant bedrock-type material, ditches normally da <br />not require lining. Culverts will be designed and installed to minimize the runoff volume <br />conveyed in each ditch. Culverts and ditches will typically be designed uein9 SED CAD to <br />predict the peak runoff end Manning's equation to determine the peak velocity and flow <br />depth (see Attachment 13-1). <br />If the ditch is not stable, Shen a larger ditch section will be used and/or adequately <br />line the ditch in order to comply with eppl icable regulations. <br />Drainage from atcess roads within the areas disturbed by mining end reclamation activities <br />(see Exhibits 13-2 and 13-3) will be constructed to meet [he requirements of 4,OS.Z and <br />such access roads will at a minimum be constructed and maintained to minimize erosion of <br />the disturbed area, Erosion control measures to be used singly or in combination include <br />but are not limited to: <br />a. Stabilizing all exposed su rf ate areas to promote a reduction in the rate and <br />volume of runoff; <br />b. Using straw dikes, riprep, check dams, berms, geotextile materials, mulches, <br />• vegetation sediment filters, contour furrows or other measures that reduce <br />overland flow velocity, reduce runoff volume, or trap sediment; or <br />e. Such other measures to minimize erosion resultant siltation end disturbance to <br />the prevailing hydrological balant e. <br />Surfacing. See Exhibit 13-10 for typical detail. <br />Culverts. Each access road will be designed, constructed, end maintained to have adequate <br />drainage using ditches end culverts to safely convey the peak runoff from a 10-year, <br />24-hour precipitation event to sediment ponds before being released from the permitted <br />area Csee Exhibit 13-10 for typical details of drainage structures). <br />Culverts will be installed to avoid plugging or collapse and to avoid erosion at the <br />inlets and outlets. Riprap will be installed es necessary to reduce the exit velocity. <br />The minimum width will be the width of the natural downstream channel. The riprep wilt be <br />sized in [he field by Peabady's project .engineer based on the "as-built" slope of the <br />culvert and final configuration of the exit channel slope area. The sizing shall be based <br />• on the Federal Highway Administration's HEC No. 11 "Use of Riprap for Bank Drotection" or <br />other standard methods. All pipes will have a minimum cover of 12 inches. Culverts and <br />33 Revised 04/24/91 <br />