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• will be revegetated to control runoff. In an area where revegetation would not be sufficient to <br />control erosion, the area will be rip-rapped. Temporary measures to reduce erosion will be <br />employed while the area is undergoing revegetation such as straw dikes, containment ditches, <br />etc. WFC typically constructs ditches on the inside of roadway cuts and safety berms for <br />drainage. As most road cuts are into resistant bedrock-type material, ditches normally do not <br />require lining. Culverts will be designed and installed to minimize the runoff volume conveyed <br />in each ditch. Culverts and ditches will typically be designed using SEDCAD or other generally <br />accepted software to predict the peak runoff and Manning's equation to determine the peak <br />velocity and flow depth. ' <br />If the ditch is not stable, then WFC will use a larger ditch section and/or adequately line the <br />ditch in order to comply with applicable regulations. <br />Drainage from haul roads within the areas disturbed by mining and reclamation activities (see <br />Map 2.05.3-1) will be constructed to meet the requirements of 4.05.2 and such haul roads will <br />at a minimum be constructed and maintained to minimize erosion of the disturbed area. <br />Erosion control measures to be used singly or in combination include but are not limited to: <br />a. Stabilizing all exposed surface areas to promote a reduction in the rate and <br />• volume of runoff; <br />b. Using straw dikes, riprap, 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 />c. Such other measures to minimize erosion resultant siltation and disturbance to <br />the prevailing hydrological balance. <br />Culverts will be installed to avoid plugging or collapse and to avoid erosion at the inlets and <br />outlets. Riprap will be installed as necessary to reduce the exit velocity. The minimum width <br />will be the width of the natural downstream channel. The riprap will be sized in the field based <br />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 <br />Bank Protection" or other standard methods. All pipes will have a minimum cover of 12 inches. <br />Culverts and drainage ditches will be maintained periodically to prevent accumulation of debris <br />on the culverts inlets and outlets. <br />• The following is an outline of the general design procedures used in the design of culverts: <br />(REVISED Y2/00) 2.05.3(3) -15 <br />