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for Grassy Creek. Table 14 provides a comparison of those standards to <br />water quality data collected this year from NPDES and stream sites in <br />the Grassy Creek basin. Standards that were exceeded are: <br />Parameter <br />Iron, Total Rec. <br />Nitrite <br />Selenium <br />Sulfide <br /># of Sites / # of Excursions <br />4/4 <br />2/3 <br />1/1 <br />3/3 <br />All iron excursions were the result of high suspended solids. None of <br />the iron excursions were at a NPDES site. The two stream sites that <br />experienced excursions are upstream of Seneca's discharges. <br />Two stream sites, SSG1 and SSLG5, exceeded the nitrite standard. Both <br />sites are upstream of the Seneca II mining area. Nitrites are unstable <br />in aerated water and will oxidize into nitrates (Hem, 1989). <br />Three samples experienced exceedances of the sulfide standard (0.002 <br />mg/l un-ionized). One exceedance was from NPDES3. 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). One excursion of <br />effluent limits occurred this year. There was chronic WET test failure <br />(C. dubia only) at Discharge Point 008 with a value of 25%. The IWC for <br />this site is 100%. Samples were collected from July 28 to August 1. The <br />P. promelas test passed with a value >100%. A Preliminary Toxicity <br />Investigation (PTI) was conducted by The SeaCrest Group in Louisville, <br />CO. The PTI indicates no toxicity present in the outfall. Since the PTI <br />showed no toxicity, the toxicity incident was closed. Details of this <br />incident may be found in the cover letter for the third quarter <br /> <br /> <br />• <br />20