2012-05-24_REPORT - C1980005 - Laserfiche WebLink

Home Browse Search

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 Iron, Total Rec. 2/2 Nitrite 1/1 Selenium 1/3 All iron excursions (standard 1.0 mg /1) were the result of high suspended solids in Fish Creek. One sample from Fish Creek exceeded the nitrite standard. Nitrites are unstable in aerated water (Hem, 1989), and will oxidize to nitrates. No excursions occurred at NPDES outfalls. Three samples from NPDES8 exceeded the chronic selenium receiving stream standard, 4.6 ug /l (potentially dissolved), with a values of 5.9 ug /l in April, 17 ug /l in May and 10 ug /l in June. Values were no greater than 2 ug /l for the rest of the year. The acute receiving stream standard, 18.4 ug /l (potentially dissolved), was not exceeded. See the following NPDES Effluent section for a discussion of these excursions. No sites exceeded the sulfide standard this year. The sulfide values provided in Tables 13 and 15 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: http: / /www.mullalyengineexing.com.au /images /product /file /Problem of Hydr o en Sulphide in Sewers. df page 5, Table 1. The results of those calculations are presented in Tables 13 and 15 of this AHR. The 11