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tractive forces that cause erosion. Temporary diversions in place longer than a growing season <br />will be seeded with a temporary seed mix as outlined in Section 2.05.4(2)(e). Diversions have <br />been designed to maximize geomorphic stability while minimizing disturbance. All temporary <br />diversions will be removed and reclaimed after mining activities have been completed. Plans <br />have been developed for water rights augmentation pumping that will meet effluent limitations <br />and minimize erosion. Drainage from haulage and access roads will be routed to the sediment <br />pond. Where necessary, culverts will be designed and constructed using approved engineering <br />design criteria to minimize erosion and prevent the contribution of additional sediment to runoff. <br />Surface Water Quantity The Operations Plan - New Horizon North (Map 2.05.3 -1) details <br />pond diversion and culvert locations that will control all drainage into, through, and out of New <br />Horizon North mining area. Surface water flow at NHN is primarily the product of seasonal <br />irrigation, (See Section 2.04.7). The 2 n Park Lateral will be diverted through a HDPE pipeline <br />around the mining area. Once mining has advanced far enough to the north, the HDPE pipeline <br />will be moved to the approximate original 2nd Park Lateral right -of -way. Down stream irrigation <br />water flow will not be interrupted. The plan has been developed for insuring that changes in <br />surface water quantities are minimized. The impact of designed structures proposed for the New <br />Horizon North mining area (sediment pond, diversion ditches, culverts, etc.), was determined to <br />have no significant effect on surface water quantity (see Probable Hydrologic Consequences at <br />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 <br />this capacity by dewatering and /or excavating excessive sediment accumulated according to <br />plans outlined in Section 2.05.3(3), Mine Facilities. The bottom and sides of the sediment pond <br />will be compacted to a sufficient density to prevent leakage of pond water to the shallow bed <br />rock zones. This method has been successful at the adjacent New Horizon Mine. <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 drainage -ways will insure that runoff <br />originating within or outside each mining area will be controlled and adequately routed through <br />to minimize changes in surface water quantities. <br />The post mining landscape is designed to protect the hydrologic balance by establishing slopes <br />that generally will not exceed 5:1. Any highwall reductions will result in maximum slopes not to <br />exceed 5:1. Reclaimed hillsides proposed for the New Horizon North mining area approximate <br />the original pre- mining contours. <br />Topsoil material will exhibit infiltration rates generally similar to pre- mining soils. At the NHN <br />Mine, future reclaimed areas will be manipulated mechanically using chisel plowing and ripping <br />of graded and top - soiled areas in combination with timely reseeding to minimize overland flow <br />rates and volumes. <br />Section 2.05.6(3) Page 6 October 2013 (TR -05) <br />E: \New Horizon \DRMS \NHN Perm it \04 Technical Revisions TR \TR -05 \Documents from Jason \2.05.6(3) Protection of Hydrologic Balance_TR- 05.doc <br />