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Surface Water Quantity <br /> Map 2.05.3(3)-1 details pond diversion and culvert locations that will control all drainage into, <br /> through, and out of New Horizon 2 mining area. The plan has been developed for insuring that <br /> changes in surface water quantities are minimized. The impact of designed structures proposed <br /> for the New Horizon 2 mining area (sediment pond, diversions, culverts, etc.), was determined to <br /> have no significant effect on surface water quantity(see Probable Hydrologic Consequences at the <br /> end of this section). <br /> The sediment ponds have been designed according to acceptable engineering criteria to contain <br /> (at a minimum)the 10-year, 24-hour runoff volumes. WFC will ensure that the ponds maintain this <br /> capacity by dewatering and/or excavating excessive sediment accumulated according to plans <br /> outlined in Section 2.05.3(3), Mine Facilities. The bottom and sides of the sediment pond will be <br /> compacted to a sufficient density to prevent excessive leakage of pond water to the shallow <br /> aquifers. <br /> Diversions have been designed to pass the 10-year, 24-hour runoff volumes in accordance with <br /> approved engineering design criteria. Culverts and road drainageways will insure that runoff <br /> originating within or outside each mining area will be controlled and adequately routed through to <br /> minimize changes in surface water quantities. <br /> The postmining landscape is designed to protect the hydrologic balance by establishing slopes that <br /> generally will not exceed 5:1. Any highwall reductions will result in maximum slopes not to exceed <br /> 5:1. Reclaimed hillslopes proposed for the New Horizon 2 mining area approximate the original <br /> premining contours. <br /> Topsoil material will exhibit infiltration rates generally similar to premining soils. At the New Horizon <br /> Mine, future reclaimed areas will be manipulated mechanically using chisel plowing and ripping of <br /> graded and topsoiled areas in combination with timely reseeding to minimize overland flow rates <br /> and volumes. <br /> Revised March 2015 (TR-68) 2.05.6(3)-9 <br />