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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 />http://www.mullalyen ineerin .com.au/ima es/ roduct/file/Problem of Hydr <br />ogen Sulphide in Sewers.pdf page 5, Table 1. No excursions of the 0.002 <br />mg/l un-ionized sulfide standard occurred this year. <br />The aquatic life ammonia standard is dependent on pH and temperature. <br />The detection limit for ammonia is 0.05 mg/l. All values above detection <br />limit are compared to table standards found on this website, page 87: <br />http://www.epa.gov/waterscience/criteria/ammonia/99update.pdf <br />No ammonia excursions occurred this year. <br />SCC runs two different mercury tests, a high level test with a MDL of <br />0.2 ug/l (for streams and NPDES sites) and a low level test with a MDL <br />of 0.0002 ug/l (for NPDES sites only). All high level test values (both <br />stream segments) this year were less than 0.2 ug/1. All low level tests <br />(both stream segments) were below the 0.01 ug/l stream standards. 0 <br />NPDES Effluent Criteria (Permit No. CO-0000221). Two excursions of NPDES <br />effluent criteria occurred this year. On April 12, a TR iron value of <br />1.95 mg/l was observed at NPDES6. On April 14, a TR iron value of 1.04 <br />mg/l was observed at NPDESI6. Normally, the standard is 1.0 mg/1. <br />However, in August 2008, the Colorado Water Quality Control Commission <br />authorized a temporary modification for the total recoverable iron <br />standard to be set at "existing quality" for Yampa Segment 13d, Dry <br />Creek, to which these outfalls discharges into. Therefore, these <br />excursions should not be considered NPDES violations. Also, as discussed <br />above in the previous section, the new ambient-based standard for this <br />stream segment in April will be 3.04 mg/1. These excursions were most <br />likely caused by snowmelt runoff. <br />Surface Water Summary. Flow values from NPDES ponds were above average <br />this year at all ponds except Ponds 005 and 009. TDS values at NPDES <br />Pond 006 are increasing, as are TDS values at downstream surface water <br />Sites WSHF1, WSDS, and all Spoil Springs except #5. The TDS trend is <br />22