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~1 <br />before it is diverted and used for irrigation. No irrigation exists on <br />Grassy Creek below Seneca II. Due to the relative amount of dilution by <br />additional water from both sources, the ambient water qualities of Fish <br />Creek and the Yampa River are the dominant factors in determining their <br />suitability for irrigation. Water discharged from the Seneca II Mine <br />is, however, used for livestock watering. <br />Surface Water Summary. Below average rainfall and snowfall values <br />resulted in below average discharge values this year. TDS values at <br />NPDES 002 and 003 are increasing at a moderate rate while TDS values at <br />NPDES 004 and 008 are increasing slightly. On lower Grassy Creek <br />(SSG2), TDS values display a stable trend. Of the nine spoil springs <br />monitored, two are exhibiting decreasing EC trends, while three display <br />a stable EC trend. Discharges are normally suitable for livestock, but <br />Sometimes exceed water quality standards for irrigation. <br />One exceedence of NPDES effluent criteria -(Permit No. CO-0000221) <br />occurred this year. NPDES 003 experience an excursion of the 30 day <br />average total suspended solids (TSS) limit of 35 mg/1 with a value of 38 <br />mgll measured from a sample collected September 12. However, a retest of <br />that sample resulted in a TSS value of only 8 mg/1. The TSS value on a <br />sample collected on October 16, 2001 was back down to only 6 mg/1. <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 />Buchanan and Sumers. 1968. "Stage Measurements at Gaging Stations". <br />i Colorado Dept. of Health. March 1999. "Regulation No. 31, The Basic <br />Standards and Methodologies for Surface Water" <br />21 <br />