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• streamflow conditions. By deferring discharge from ponds until flows have <br />subsided following major storm events, ponds can function as flood control <br />structures, extending the period of effective flow while minimizing peak <br />flows and consequent downstream erosion. <br />Retention of dead storage volume which amounts to approximately 4.01 acre <br />feet for all mine area ponds and 1.73 acre feet for loadout area ponds <br />will not significantly effect surface flow quantities. Based upon EFCI's <br />site experience, sedimentation ponds are normally dry or nearly dry during <br />late fall or early winter. With spring snowmelt and resulting runoff, <br />sedimentation ponds fill and some dead storage volume is established. <br />Dead storage volume normally fluctuates throughout the spring and summer <br />months in response to evaporation and storm events. <br />Because dead storage volume is normally established during spring snow- <br />melt, reductions in downstream flows are not significant since flows in <br />area drainages exceed any water use requirements. Actual peak irrigation <br />• requirements normally lag spring runoff by approximately two (2) to three <br />(3) months. Consequently, loss of dead storage volume during spring <br />runoff has no effect on downstream water users. <br />Upon completion of mining and related activities, reclamation will have <br />the effect of significantly reducing surface runoff volumes within <br />disturbed areas. While this may have limited and localized effects on <br />surface flows, it will effectively reestablish natural infiltration and <br />runoff conditions. The long term result will be surface runoff and <br />streamflows which are approximately the same as prior to initiation of <br />mining operations. <br />EFCI's planned mining, processing, and related activities have the <br />potential to temporarily reduce groundwater levels, alter groundwater flow <br />patterns and characteristics, and increase groundwater storage capacity. <br />As underground mining operations progress, groundwater inflows will result <br />• in some localized drainage of groundwater resources in the interval to be <br />mined. In addition, where subsidence fractures intersect overlying <br />abandoned mine workings, drainage from the flooded workings has the <br />2.05.6-31 <br />