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• Parameter # of Sites / # of Excursions <br />Iron 4/5 <br />Nitrite 2/2 <br />Selenium 3/5 <br />The iron standard (1.0 mg/1) was exceeded five times this year. <br />Excursions were normally related to high suspended solids. Both NPDES <br />site excursions occurred during snowmelt runoff in April. This strict <br />aquatic life standard was exceeded in 38~ of the premining stream <br />samples. Two samples also exceeded the nitrite standard. Nitrites are <br />unstable in aerated water (Hem, 1989), and will oxidize to nitrates. <br /> Two samples had cadmium values that were less than an elevated detection <br /> limit (5 ug/1 vs. a normal d etection limit of 0.5 ug/1), which was <br /> higher than the CDOH standard of 1.2 ug/l. The same two samples had <br /> copper values with elevated detection lim its. The cause of these <br /> elevated detection limits was a decision by th e laboratory to dilute the <br />. samples prior to analyses in order to reduce the effects of <br /> interferences (primarily, high salinity). <br />Five samples from three sites exceeded the chronic selenium standard, <br />4.6 ug/1. The acute standard, 18.4 ug/1, was not exceeded. One site <br />(NPDESI0) had an elevated detection limit that was higher than the <br />standard. <br />Four samples from three sites experienced exceedances of the sulfide <br />standard (0.002 mg/1 un-ionized) this year. 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 />NPDES Effluent Criteria (Permit No. CO-0000221). No excursions of NPDES <br />• effluent criteria occurred this year. <br />14 <br />