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Iron, Total Rec. 6/16 <br />Mercury 1/1 <br />Nitrite 2/2 <br />Sulfide 4/6 <br />Only two of the sixteen iron exceedances were from NPDES sites. They <br />were likely due to high suspended solids values normally observed during <br />snowmelt runoff. This strict aquatic life standard (1.0 mg/1) was <br />exceeded in over half of the premining stream samples. <br />Six samples experienced exceedances of the sulfide standard (0.002 mg/1 <br />un-ionized) this year. Only one of these exceedances was from a NPDES <br />site. All exceedances were associated with high suspended solids. The <br />analytical method available to SCC detects both dissolved sulfides and <br />acid-soluble metallic sulfides present in suspended matter. It is <br />suspected that a large portion of the sulfides detected is of the latter <br />type, which would bias the un-ionized results high. Any dissolved <br />sulfides present in surface water should eventually oxidize to sulfates. <br />One site on lower Hubberson Gulch exceeded the mercury standard, 0.01 <br />ug/l. It is not an NPDES site. <br />Two sites on Hubberson Gulch exceeded the nitrite standard, 0.05 ug/1. <br />Neither is an NPDES site. Nitrites are unstable in aerated water and <br />will oxidize into nitrates (Hem, 1989). <br />The stream standards for Segments 13d and e discussed above are based on <br />aquatic life standards, even though there are no fish present in the <br />upper portions of these drainages. SCC has proposed to the CDPHE that <br />these stream standards be changed to agricultural standards. A decision <br />regarding this will be made in June 2008 at a hearing for the Upper <br />Colorado River Basin. <br />NPDES Effluent Criteria (Permit No. CO-0000221). No excursions of NPDES . <br />effluent criteria occurred this year. <br />?_2 <br />