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Sediment Loading <br />All runoff from areas disturbed during the life of mine will pass through one <br />of five sedimentation ponds prior to leaving the permit area. Discharges from <br />the ponds will be required to meet NPDES effluent limits, and should, <br />therefore, not contribute additional suspended solids to stream flows neaz the <br />permit area. <br />Following reestablishment of drainage channels and vegetation during <br />reclamation, more runoff from the mine area will occur. However, sediment <br />loads in that runoff should be no larger than those currently coming from the <br />permit area. <br />Ouan[ity of Surface Flows <br />The largest peak flow recorded in Annand Draw during baseline data <br />collection was 0.585 cfs. The presence of a sediment pond in Annand Draw <br />will attenuate peak flows in that drainage during mining. After mining, flows <br />in Annand Draw will increase due to establishment of spoil springs and <br />additional runoff from the reclaimed area. Spoil springs are projected to add <br />approximately 0.073 cfs of base flow to Annand Draw. <br />Spoil springs in Annand Draw and the Pond l l drainage will add year-round <br />base flow to Grassy Creek. These spoil spring contributions are projected to <br />increase mean flows during irrigation season (June 1-September 30) in <br />Grassy Creek from 0.25 to 0.37 cubic feet per second downstream from the <br />Yoast Mine. <br />Spoil springs are projected to add approximately 0.159 cfs of base flow to <br />Sage Creek during irrigation season (June 1 -September 30). These spoil <br />spring contributions are projected to increase mean flows during the irrigation <br />season in Sage Creek from 0.259 to 0.418 cfs. <br />Ouality of Surface Water <br />The primary impact of Yoast mining operations on surface water quality will <br />be an increase in total dissolved solids concentration resulting from the <br />occurrence of spoil springs after backfilled spoil in the mine pits has become <br />saturated. Using conservative assumptions regarding the amount of inflows <br />to the reclaimed pits, and the quality of spoil spring water, and information <br />gathered from the nearby Seneca II Mine in recent years, Seneca Coal <br />Company has estimated the changes in surface water quality which may be <br />caused by the proposed Yoast Mine. The projected impacts on each of the <br />affected drainages near [he permit area are summarized below. <br />Your Mme ~7 March 6, ?001 <br />