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~- from the mine is significantly diluted by water from either Fish Creek or the Yampa River before it is diverted and used for irrigation. No irrigation exists on Grassy Creek below Seneca II. Due to the relative amount of dilution by additional water from both sources, the ambient water qualities of Fish Creek and the Yampa River are the dominant factors in determining their suitability for irrigation. Water discharged from the Seneca II Mine is, however, used for livestock watering. TDS values at NPDES 002 and 003 are increasing at a moderate rate while TDS values at NPDES 004 and 008 are increasing slightly and appear to be stabilizing. On lower Grassy Creek (SSG2), TDS values are increasing. Of the ten spoil springs monitored, one (SSSPGIOA) exhibits an increasing EC trend, seven are exhibiting decreasing EC trends, while two display a stable EC trend. NPDES discharges are normally suitable for livestock and irrigation, but sometimes exceed water quality standards for aquatic life. A 76 mg/1 increase in TDS was predicted by the PHC for Fish Creek in June, while a 30 mg/1 increase was observed at Site SSF13. TDS values at lower Grassy Creek (SSG2) were above predicted values, most likely due to lower than normal stream flows. Although the annual precipitation for this year was above average, only one of the four NPDES sites, NPDES2, exhibited an annual average flow above the historic averages. References American Public Health Association (Ed.). 1985. "Standard Methods for the Examination of Water and Wastewater", 16th Edition, Washington, D.C. Brakensieh and others. 1979. "Field Manual for Research in Agricultural Hydrology". Buchanan and Sumers. 1968. "Stage Measurements at Gaging Stations". Colorado Dept. of Health. August 2005. "Regulation No. 31, The Basic Standards and Methodologies for Surface Water" 23