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4.6.2.3 Protection of the Hydrologic Balance <br />4.6.2.3.1 Diversion and Conveyence of Overland Flow <br />Unit Train Loading Area <br />Runoff from the railroad bed is directed toward drainage swales which <br />run parallel to the tracks for the entire length of the railroad spur. <br />Cut and fill along the railroad spur has been performed to achieve <br />drainage toward the center of the crescent where a sediment/storm <br />water pond is located. The flow direction in the drainage swales is <br />indicated on Drawing D-2-4. All disturbed area runoff from the <br />railroad bed is collected in these drainage swales and routed to <br />Sediment Pond 1. Atypical cross-section of the railroad bed and the <br />drainage swales is shown on Drawing D-2-4. The drainage swales are <br />trapezoidal in shape with 2h:ly side slopes and a bottom width of <br />1-foot. The discharge ca pactiy of each drainage Swale is approxima- <br />• tely 10 cfs on the 0,5 percent grade. Design calculations for the <br />diversion structures are given in Appendix 4-B. <br />The direction of overland flow at the loadout facility from those <br />areas outside the permit boundary are also shown on Drawing D-2-4. <br />These directions of flow correspond to the pre-construction directions <br />of flow. The overland flow from the undisturbed areas at the facility <br />is prevented from entering the drainage channels parallel to the <br />railroad by berms which are 2-feet above the existing grade. This <br />ensures that runoff from the undisturbed area is not mixed with runoff <br />from the disturbed area along the railroad spur, <br />Conveyor <br />Overland flow beneath the conveyor will continue approximately in its <br />predevelopment path toward the Roaring fork River. The disturbed area <br />• <br />4-132 <br />