2014-02-05_REPORT - C2009087 - Laserfiche WebLink

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would bias the un- ionized results high. Any dissolved sulfides present in surface water should eventually oxidize to sulfates. No sites exceeded the ammonia standard this year. The aquatic life ammonia standard is dependent on pH and temperature. The detection limit for ammonia is 0.05 mg /1. All values above detection limit are compared to table standards, page 87, found on this website: http:/ /www.epa.gov /waterscience/ `criteria /ammonia/99update.pdf The drinking water standard for mercury is 2 ug /1. The aquatic life standard for mercury is 0.01 ug /1, which is set to protect the average human consumer of fish. PSCM's lab uses a method with a detection limit of 0.2 ug /1. None of the samples collected this year were above the detection limit. During the last NPDES permit renewal, the CDPHE performed a reasonable potential analysis on PSCM's outfalls. It determined that there was no reasonable potential for PSCM's outfalls to exceed the mercury limit; therefore, mercury monitoring is no longer required for PSCM's outfalls. NPDES Effluent Criteria (Permit No. CO- 0000221) . Three excursions of effluent limits occurred this year, all of which involved the chronic selenium standard, 4.6 ug /1. The Outfall 003 (NPDES3) value was 4.9 ug /1 in April 2013. Outfall 004 (NPDES4) values were 4.9 ug /l in April 2013 and 6.4 ug /l in May 2013. The selenium limit stated both on the DMR and the discharge permit (issued 3/31/10) for Outfall 003 is 4.6 ug /1. However, the Reasonable Potential (RP) analysis performed for this permit (in the rational dated 2/4/10 by Andrew Nuehart) indicates that selenium should be `monitored' only. Therefore, we feel that the limit set in the permit is incorrect. Furthermore, this is the first excursion of the 4.6 ug /l selenium standard since monitoring began at this outfall in 1980. The highest previous values were 4.0 ug /l total recoverable on 6/10/96 and 3.1 ug /l potential dissolved on 3/9/11. 19