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This arrangement allows for the capture of surface water that contacts maintenance or <br /> processing operations and provides a secondary containment design for the operations area. <br /> The pond has been designed to contain approximately 26,555 cubic feet of water with five <br /> feet of freeboard. This storage capacity will store estimated seepage from the tailing's <br /> facility. Estimated contact water runoff from the 10-year, 24-hour storm event would also <br /> be contained by the pond, assuming the reclaim pumping system is operational. The contact <br /> water pond as sized would be classified as a non jurisdictional size dam by the Colorado <br /> Division of Water Resources as its capacity is less than 100 acre-feet and the dam height <br /> is less than 10 vertical feet as measured from the lowest point of the natural ground surface <br /> to the spillway crest(CDWR, 2007). <br /> Onsite Stormwater Impacts (Basin B, C and F) <br /> The laydown area, topsoil and overburden stockpile areas, and access road improvements <br /> are included within this area. <br /> The laydown area has stepped gravel pads with a 1 to 2 percent slope where equipment and <br /> materials will be stored. Topsoil and overburden stockpiles will be sloped at 3:1 (h:v). <br /> Materials from both stockpiles will be used for mine reclamation. <br /> The access road from Temple Canyon Road will be located east of the laydown and <br /> stockpile areas. Culverts are shown on the design drawings at strategic locations to direct <br /> surface water between these areas and into Channel C: Onsite Stormwater Diversion <br /> Channel. <br /> Increases in surface water flows were calculated using the rational method as required in <br /> Fremont County regulations for basins smaller than 20 acres. Tables 2 and 3 below shows <br /> historical flows and flows after improvements are made to the operations, laydown, and <br /> stockpile areas for a 10-year storm and 100-year storm frequency respectively. <br /> Table 2— Undeveloped and Developed Flows (10-Year Storm Frequency) <br /> Area (basin) Calculation Undeveloped Developed Flow <br /> Method historical flows cfs Flows cfs Change cfs <br /> Operations B Rational 18.81 0 -18.81 <br /> Laydown, Rational 22.24 45.22 22.98 <br /> Stock iles C <br /> Access Road (F) Rational 19.24 25.32 6.08 <br /> Totals for the 10-year storm event: 60.29 70.54 10.25 <br /> N <br /> N <br /> O <br /> N <br /> 00 <br /> N <br /> c-I <br />