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Drainage from haul roads within the areas disturbed by mining and reclamation activities (see <br />Map 2.05.3(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. Erosion <br />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 the <br />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 will <br />be the width of the natural downstream channel. The riprap will be sized in the field based on the <br />"as -built" slope of the culvert and final configuration of the exit channel slope area. The sizing <br />shall be based on the Federal Highway Administration's HEC No. 11 "Use of Riprap for Bank <br />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 />1. Identify the need for a structure from topographic maps, and a visit to the site; <br />2. Determine the size and hydrology of the watershed in question; <br />3. Perform SEDCAD, or other acceptable software, computer run to determine the peak <br />runoff from a 10 -year, 24-hour precipitation event. <br />4. Using SEDCAD, or other acceptable software, computer run to determine the proper size <br />of culvert to handle the peak runoff form a 10 -year, 24 hour precipitation event. Also <br />check the pipe sizing using the hydrograph of corrugated steel pipe culverts with inlet or <br />outlet control, the discharge quantity and the amount of entrance head desired. <br />Section 2.05.3(3) Page 21 April 2017 (MR -104) <br />