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<br />Surface Water Summary <br />The Yoast Mine PHC (PAP Tab 17, Attachment 17-5) predicts TDS increases <br />to be observed at various stream sites during the irrigation season <br />(June-September). The following table outlines those predictions along <br />with this year's observed averages. This table indicates that no TDS <br />predictions were exceeded this year. <br />Stream Site Predicted TDS values (mg/1) This years average TDS (mg/1) <br />YSGF5 1337 975 <br />NPDESIO 3938 1790 <br />NPDESI2 4291 3932 <br />WSSF3 (Seneca II-W site) 2118 780 <br />No sites exceeded the PHC predictions. TDS trends are increasing at <br />Spoil Spring 1, NPDE512 and two downstream stream sites (YSS2 and <br />YSGF5). TDS values have recently decreased at NPDESIO and 11, and have • <br />stabilized at Site YSGS. Average flow values this year were below <br />historic averages at Ponds 011 and 012, but were above average at Pond <br />010. <br />Water discharged from the Yoast Mine is not used directly for <br />irrigation. Indirectly, although, wa r_er 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 dilution, the ambient water qualities of Grassy <br />Creek, Sage Creek, and the Yampa River are the dominant factors in <br />determining their suitability for irrigation. Water discharged from the <br />Yoast Mine is, however, used for livestock watering. NPDES discharges <br />are normally suitable for livestock and irrigation, but sometimes exceed <br />water quality standards for aquatic life. <br />References <br />CJ <br />15 <br />