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Stream Site Predicted TDS values <br />YSGFS 1337 <br />NPDESIO 3936 <br />NPDESI2 4291 <br />WSSF3 (Seneca II-W site) 2118 <br />This years average TDS (mq/1) <br />905 <br />2313 <br />4303 (3955 calculated) <br />755 <br />One site exceeded the PHC predictions. NPDE512 had an average TDS value <br />of 4303 mg/1, which exceeded the predicted value of 4291 mg/1 by 12 mg/1 <br />(<1~) However, the calculated TDS average for NPDESI2 was 3955 mg/1, <br />which is below the predicted value. <br />TDS trends are increasing at Spoil Spring 1, NPDESII and NPDESI2 and two <br />downstream stream sites (YS52 and YSGFS). TDS values have decreased at <br />NPDESI3, and have stabilized at NPDESIO and Site YSGS. Average flow <br />values this year were above historic averages at Ponds 010, 011 and 012. <br /> water discharged from the Yoast Mine is not used directly for <br />• irrigation. Indirectly, although, water discharged from the mine is <br /> significantly diluted by water from Grassy Creek, Sage Creek, or the <br /> Yampa River before it is diverted and used for irrigation. Due to the <br /> relative amount of dilu tion, the ambient water qualities of Grassy <br /> Creek, Sage Creek, and the Yampa River are the dominant factors in <br /> determining their suitabi lity for i rrigation. Water discharged from the <br /> Yoast Mine is, however, used for l ivestock watering. NPDES discharges <br /> are normally suitable for livestock and irrigation, but sometimes exceed <br /> water quality standards for aquatic life. <br />References <br />American Public Health Association (Ed.). 1985. "Standard Methods for <br />the Examination of Water and Wastewater", 16th Edition, Washington, D.C. <br />Brakensieh and others. 1979. "Field Manual for Research in Agricultural <br />Hydrology". <br />• Buchanan and Somers. 1968. "Stage Measurements at Gaging Stations" <br />15 <br />