2013-02-20_REPORT - C1980005 - Laserfiche WebLink

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region, a more appropriate (EPA) standard would be 10 mg /l. The maximum manganese value observed this year at any surface water site was 0.745 mg /l. Table 12 shows the CDPHE receiving stream standards for Fish Creek (Yampa Segment 13b). Table 13 provides a comparison of those standards to water quality data collected this year from NPDES and stream sites in the Fish Creek basin. The stream standards for Fish Creek are based on aquatic life standards, even though there are no fish present in the upper portion of the tributary that NPDES8 discharge into. Standards that were exceeded are: Parameter # of Sites / # of Excursions Sulfides 1/1 One site, Spoil Sprang 9, exceeded the sulfide standard (0.002 mg /1) this year,, with a value of 0.005 mg /l. The sulfide values provided in Table 13 differ from the values reported in Appendix D. The sulfide data presented in Appendix D are the total of both the ionized (S -) and un- ionized (H2S) forms of hydrogen sulfide. The un- ionized form is the potentially toxic form, and is what the CDPHE water ,quality standard is based upon. A procedure for calculating the un- ionized form may be found on the website: htt : / /www.mullal en ineerin .com.au /ima es/ roduct /file /Problem of Hydr ogen Sulphide in Sewers.pdf page 5, Table 1. The results of those calculations are presented in Table 13 of this AHR. The analytical method detects both dissolved sulfides and acid - soluble metallic sulfides present in suspended matter. It is suspected that a large portion of the sulfides detected is of the latter type, which 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 /l. All values above detection limit are compared 11