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[~ <br />This year, no CDOH surface water agricultural use standards were <br />exceeded. Also, no exceedences of NPDES effluent criteria (Permit No. <br />CO-0000221) occurred this year. <br />Surface Water Summary <br />The Yoast Mine PHC (PAP Tab 17, Attachment 17-B) 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 (mq/1) This years average TDS (mg/1) <br />YSGFS 1337 905 <br />NPDESI0 3938 2498 <br />NPDE512 4291 1200 <br />WSS F3 (Seneca II-W site) 2118 ~~690 <br />TDS trends are increasing at all NPDES and stream sites except YS52 <br />(Sage Creek below NPDESI0). Water discharged from the Yoast Mine is not <br />used directly for irrigation. Indirectly, although, water discharged <br />from the mine is significantly diluted by water from Grassy Creek, Sage <br />Creek, or the Yampa River before it is diverted and used for irrigation. <br />Due to the relative amount of dilution, the ambient water qualities of <br />Grassy Creek, Sage Creek, and the Yampa River are the dominant factors <br />in determining their suitability for irrigation. Water discharged from <br />the Yoast Mine is, however, used for livestock watering. <br />References <br />American Public Health Association (Ed.). 1985. "Standard Methods for <br />the Examination of Water and Wastewater", 16th Edition, Washington, <br />D.C. <br />Brakensieh and others. 1979. "Field Manual for Research in <br />Agricultural Hydrology". <br />13 <br />