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effluent limits are 35 mg/1 (monthly average) and 70 mg/1 (daily max.). <br />The sample was collected during snowmelt runoff, and therefore, an <br />alternate of the TSS limit ("report") is allowed. The settleable solids <br />value was less than 0.4 ml/1. <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. <br />Stream Site Predicted TDS values <br />YSGF5 1337 <br />NPDESIO 3938 <br />NPDESI2 4291 <br />WSSF3 (Seneca II-W site) 2118 <br />No sites exceeded the PHC predictions. <br />1) This years average TDS (mg/1) <br />960 <br />2270 <br />4227 (3705 calculated) <br />815 <br />TDS trends are increasing at NPDESII, NPDESI2, NPDESI4 and three <br />downstream stream sites (YSS2, YSG5 and YSGF5) TDS values have <br />decreased at NPDESI3 and Spoil Spring 1, and have stabilized at NPDESIO. <br />Average flow values this year were above historic averages at NPDESI2, <br />but were below average at NPDESIO and NPDESII. <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 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 suitable for livestock and irrigation, but sometimes exceed water <br />quality standards for aquatic life. <br /> <br />~~ <br />• <br />14 <br />