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values observed afterwards. These excursions are most likely due to . <br />sample contamination or lab error. <br />Four samples exceeded the chronic selenium standard, 4.6 ug/1, but not <br />the acute standard, 18.4 ug/1. NPDES4 and 8 exceeded the standard on <br />April 3 and September 11. <br />Four samples experienced exceedences of the sulfide standard (0.002 mg/1 <br />un-ionized) this year. One of these excursions was from a stream above <br />Seneca's discharges. Two were from NPDES4 and 8. The analytical method <br />available to SCC detects both dissolved sulfides and acid-soluble <br />metallic sulfides present in suspended matter. It is suspected that a <br />large portion of the sulfides detected is of the latter type, which <br />would bias the un-ionized results high. Any dissolved sulfides present <br />in surface water should eventually oxidize to sulfates. <br />The stream standards for Fish Creek (13b) discussed above are based on . <br />aquatic life standards, even though there are no fish present in the two <br />tributaries that NPDES4 and NPDES8 discharge into. SCC has proposed to <br />the CDPHE that these stream standards be changed to agricultural <br />standards. A decision regarding this will be made in June 2008 at a <br />hearing for the Upper Colorado River Basin. <br />In September 2003 (effective January 2004), the CDPHE resegmented Grassy <br />Creek from Yampa Segment 12 to Segment 13e. Regulation 33 was further <br />revised in December 2005. Table 13 shows the new CDPHE receiving stream <br />standards for Grassy Creek. Table 14 provides a comparison of those <br />standards to water quality data collected this year from NPDES and <br />stream sites in the Grassy Creek basin. Standards that were exceeded <br />are: <br />Parameter # of Sites / # of Excursions <br />Iron, Total Rec. 2/3 <br />Mercury 1/1 <br />Nitrite 1/1 <br />Sulfide 1/2 <br />20 <br />