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or the Yampa River before it is diverted and used for irrigation. No <br />irrigation exists on Grassy Creek below Seneca II. Due to the relative <br />amount of dilution by additional water from both sources, the ambient <br />water qualities of Fish Creek and the Yampa Riv er are the dominant <br />factors in determining their suitability for irrigation. Water <br />discharged from the Seneca II Mine is, however, used for livestock <br />watering. <br />TDS values at NPDES 002 and 003 are increasing at a moderate rate while <br />TDS values at NPDES 004 and 008 are increasing slightly and appear to be <br />stabilizing. On lower Grassy Creek (SSG2), TDS values are increasing. <br />Of the ten spoil springs monitored, one (SSSPG7) exhibits on increasing <br />EC trend, Seven are exhibiting decreasing EC trends, while two display a <br />stable EC trend. NPDES discharges are normally suitable for livestock <br />and irrigation, but sometimes exceed water quality standards for aquatic <br />life. <br />TDS values on lower Fish Creek (SSF13) were below the PHC predicted • <br />values, while TDS values at lower Grassy Creek (SSG 2) were above <br />predicted values (most likely due to lower than normal stream flows). <br />Below average rainfall and snowfall values resulted in below average <br />discharge values from all NPDES sites this year. <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 />Buchanan and Sumers. 1968. "Stage Measurements at Gaging Stations" <br />Colorado Dept . of Health. August 2005. "Regulation No. 31, The Basic <br />Standards and Methodologies for Surface Water" • <br />24 <br />