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Quantity of Surface Flows <br /> The largest peak flow recorded in Annand Draw during baseline data collection was 0.585 <br /> cfs. The presence of a sediment pond in Annand Draw will attenuate peak flows in that <br /> drainage during mining. After mining, flows in Armand Draw will increase due to <br /> establishment of spoil springs and additional runoff from the reclaimed area. Spoil springs <br /> are projected to add approximately 0.073 cfs of base flow to Annand Draw. <br /> Spoil spring s in Annand Draw and the Pond 11 drainage will add year-round base flow to <br /> Grassy Creek. These spoil spring contributions are projected to increase mean flows <br /> during irrigation season (June 1- September 30) in Grassy Creek from 0.25 to 0.37 cubic <br /> feet per second downstream from the Yoast Mine. <br /> Spoil springs are projected to add approximately 0.159 cfs of base flow to Sage Creek <br /> during irrigation season (June 1 through September 30). These spoil spring contributions <br /> are projected to increase mean flows during the irrigation season in Sage Creek from 0.259 <br /> to 0.418 cfs. <br /> Quality of Surface Water <br /> The primary impact of Yoast mining operations on surface water quality will be an <br /> increase in total dissolved solids concentration resulting from the occurrence of spoil <br /> springs after backfilled spoil in the mine pits has become saturated. Using conservative <br /> assumptions regarding the amount of inflows to the reclaimed pits, and the quality of spoil <br /> spring water, and also using information gathered from the nearby Seneca II Mine in recent <br /> years, Seneca Property, LLC has estimated the changes in surface water quality which may <br /> be caused by the Yoast Mine. The projected impacts on each of the affected drainages <br /> near the permit area are summarized below. <br /> Armand Draw <br /> Following the occurrence of spoil springs at the Yoast Mine, the total dissolved solids <br /> (TDS) content of surface water in Annand Draw is projected to increase from 950 to 3938 <br /> mg/l. These values, and all TDS values discussed below, are mean TDS values during the <br /> irrigation season, which is considered to last from June 1 through September 30. <br /> No use is presently made of this water before it flows into Grassy Creek. Due to the <br /> minimal flows in Annand Draw, it is reasonable to assume that no future use of this water <br /> will be made, other than livestock watering. Therefore, this increase in salinity will not <br /> result in material damage. <br /> Grassy Creek <br /> An e valuation of the water quality impacts of the Yoast Mine on Grassy Creek in the <br /> permit application projects no increase in TDS in Grassy Creek downstream from the <br /> mine. This conclusion is drawn by estimating the quality of Grassy Creek water after salt <br /> loading from Yoast Mine spoil springs, and comparing that projected water quality to <br /> current water quality in Grassy Creek downstream from the Yoast permit area. Water in <br /> lower Grassy Creek currently has an average TDS of 2584 mg/l,partially due to the <br /> influence of spoil spring discharges from the Seneca 11 Mine. Seneca Property, LLC <br /> predicts that lower Grassy Creek TDS will be 2177 mg/1 after addition of Yoast spoil <br /> springs. Thus, Seneca Property, LLC concludes that TDS in Grassy Creek will not <br /> 19 <br />