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ionized form is the potentially toxic form, and is what the CDPHE water <br />quality standard is based upon. A procedure for calculating the un- <br />ionized form may be found on the website: <br />rttp: / /www.mullalyengineexing.com.au /images /product /file /Problem of Hydr <br />cgen Sulphide in Sewers.pdf page 5, Table 1. The results of those <br />calculations are presented in Tables 13 and 15 of this AHR. The <br />analytical method 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 />No sites exceeded the ammonia standard this year. The aquatic life <br />ammonia standard is dependent on pH and temperature. The detection limit <br />for ammonia is 0.05 mg /l. All values above detection limit are compared <br />to table standards, page 87, found on this website: <br />http: / /www.epa.gov /waterscience /criteria /ammonia /99update.pdf <br />NPDES Effluent Criteria (Permit No. CO- 0000221) . Seven excursions of <br />effluent limits occurred this year, all of which involved the chronic <br />selenium standard, 4.6 ug /l. Outfall 002 (NPDES2) values were 5 ug /1 on <br />April 20, 11 ug /1 on May 5, 7 ug /l on June 16, 6 ug /l on July 11 and 5 <br />ug /1 on August 8. Outfall 004 (NPDES4) values were 14 ug /1 on May 16 and <br />8 ug /1 on June 13. <br />In the previous three years (2008 - 2010), neither outfall ever exceeded <br />the 4.6 ug /l selenium limit. It is unknown as to why these exceedances <br />occurred, although we suspect it may be due to the record snowfall and <br />rainfall, and near - record snowmelt runoff that occurred in Routt County <br />this winter and spring. Perhaps that unusually high runoff somehow <br />mobilized the selenium. Selenium values at both outfalls were less than <br />the standard for the remainder of the water year. <br />Surface Water Summary Water discharged from the PSCM is not used <br />directly for irrigation. Indirectly, although, water discharged from the <br />mine is significantly diluted by water from either Fish Creek or the <br />19 <br />