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• notify the Division of Minerals and Geology (DMG) of the design change if the grout option <br />is used. <br />Ditches also route runoff around from the back of the waste bank crest and into the side <br />ditches. This crest ditch should be constructed at a 2 percent grade, a 1.5-foot minimum <br />depth, and 2:1 side slopes. Flow rates of 3.13 feet per second (fps) produced in these <br />ditches may require slope protection, but since their position changes with the development <br />of the <br />waste bank, it is suggested that slope protection be placed if the waste bank crest is not <br />expected to advance for an extended period. <br />An upland diversion ditch needs to be constructed above the coal mine waste bank and the <br />cover fill stockpile site to manage flows from the upland watershed. This upland ditch can <br />be constructed along an existing road above the waste bank. The ditch should be constructed <br />as shown on Drawing 95266-02 to discharge to the west and east of the proposed waste <br />bank. The minimum depth should be 1.5 feet, with 2:1 side slopes. An upland diversion also <br />will be required above the cover fill stockpile. It must have the capacity to carry overland <br />. flow from the natural watershed, plus discharge from the waste bank upland diversion, for <br />a total of 26.8 cfs. The ditch should have a minimum depth of 2 feet, with 2:1 side slopes. <br />Riprap slope protection will be required to prevent scour of these ditches. The slope <br />protection requirements are provided on Drawing 95266-04. <br />A ditch system at the toe will accumulate flow from side ditches and then route this combined <br />flow to the sediment pond. The toe ditch will be a minimum of 1.5 feet deep, with 2:1 side <br />slopes. The toe to pond ditch transports flows from the toe ditch to the sediment pond and <br />will be a minimum of 3 feet deep, with 2:1 side slopes. Riprap slope protection requirements <br />are shown on drawing 95266-04. A CMP culvert no smaller than 24 inches in diameter <br />should be placed in the toe to pond ditch, as shown on Drawing 95266-02, to permit vehicle <br />crossing. The culvert as designed has the capacity to convey the 1.5 ft flow depth. One foot <br />of cover fill is required to protect the culvert from traffic, and a Concrete headwall should be <br />constructed at the inlet and outlet to prevent erosion. The culvert will discharge 18.36 cfs <br />flowing at the 1.5 ft depth, which is greater than the ditch capacity of 12.88 cfs. Where the <br />toe to pond ditch discharges into the sediment pond, the pond embankment slope will be <br />• protected with 1-foot diameter riprap which is grouted into place. This slope protection is <br />96266/1424.RPT Coel Mine Weete Benk Final Design for the Bowie No. 2 Mine <br />June 1998 WESTEC 11 <br />ADEQUACY-Ol <br />