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LIGHT USE ROAD - DRAINAGE <br />A borrow ditch along the inside (uphill side) of the light use road will be <br />used to drain runoff from the area above the road into Sylvester Gulch. The <br />ditch presently exists as do four (4) cross-drainage corrugated metal pipes <br />(L1~' s). The Ci~'s are twelve (12) inch diameter pipes. No problems have <br />been encountered previously with drainage or erosion of the road and ditch. <br />The cross drainage C1~ outfall points have been rip-rapped to prevent <br />erosion. As shown on Drawing SGF-04, two additional cross-drainage culverts <br />(12"0) will be installed. <br />Peak discharges have been calculated for seven {7) borrow ditch segments. A <br />typical ditch design has been calculated and is shown on Drawing SGF-04. The <br />• ditch design was based on the largest drainage area which also had the least <br />amount of ditch slope. Cross drainage culverts have been located at points <br />along the road where natural drainages and/or seeps occur and also to prevent <br />the ditch from exceeding the flow at peak discharge for a 10 yr., 24 hr. event <br />of the largest drainage area (See segment 6, 32.0 acres, Drawing SGF-04.). <br />The light use road drainage system has been designed in accordance with <br />Section 4.03.3(4) of the CMLRB coal mining regulations for a 10 yr., 24 hr. <br />precipitation event. <br />LIGHT-USE ROAD - CONSTRUCTION <br />The light-use road currently exists from new State Highway 133 to the <br />Sylvester Gulch Fan Site and beyond. The road currently is a crushed gravel <br />(1} <br />