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Surface Water Quantity <br />The Operations Plan -New Horizon 2 (Map 2.05.3-1) details pond diversion and culvert locations <br />that will control all drainage into, through, and out of New Horizon 2 mining area. The plan has <br />been developed for insuring that changes in surface water quantities are minimized. The impact <br />of designed structures proposed for the New Horizon 2 mining area (sediment pond, diversions, <br />culverts, etc.), was determined to have no significant effect on surface water quantity (see Probable <br />Hydrologic Consequences at the 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 similarto premining soils. Atthe 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 />Surface Water Monitoring <br />WFC will continue to collect data from the currently approved monitoring sites. See Section 2.04.7. <br />The current Surface Water Monitoring Plan employed to monitor the extent and magnitude of any <br />mining impacts is discussed in Section 2.04,7.1 Hydrology Description. <br />• (REVISED 6/01) 2.05.6 (3) - 7 <br />