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. NPDES Effluent Criteria (Permit No. CO-0000221). Two excursions of NPDES effluent criteria occurred this year. The first excursion occurred at Pond 005. A sample collected on April 13 had a TSS value of 50 mg/1. The effluent limits are 35 mg/1 (monthly average) and 70 mg/1 (daily max.). A retest of the sample, performed beyond the holding time, had a value of only 20 mg/1. The sample was collected during snowmelt runoff, and therefore, an alternate of the TSS limit ("report") is allowed. The second excursion occurred at Point 017. A sample collected on April 13 had a TSS value of 36 mg/l. The effluent limit is 35 mg/1. A retest of the sample, performed beyond the holding time, had a value o£ only 30 mg/1. The sample was collected during snowmelt runoff, and therefore, an alternate of the TSS limit ("report") is allowed. Surface Water Summary. Flow values from NPDES ponds were below average this year at Ponds 005, 009 and 016. Flow values from NPDES ponds were above average this year at Ponds 006, 015 and 017. TDS values at NPDES sites 006 and 017 are increasing, as are TDS values at all three downstream surface water sites (WSHF1, WSDS, and WSSF3) and Spoil Springs 2 and 3. The TDS trend is decreasing at Ponds 005, 009 and 016 and Spoil Spring 4. The TDS trend is stable at Pond 015 and Spoil Spring 1. NPDES discharges are normally suitable for livestock and irrigation, but sometimes exceed water quality standards for aquatic life. All surface water sites, except for lower Sage Creek (WSSF3), had TDS values below the PHC predictions. American Public Health Association (Ed.). 1965. "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" 23