2013-03-06_REPORT - C1982057 - Laserfiche WebLink

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Parameter # of Sites / # of Excursions Iron, Total Recoverable (TR) 3/4 Selenium 1/2 None of the iron exceedances were from NPDES sites. Two of the exceedances occurred during snowmelt runoff. They were likely due to high suspended solids (TSS) values normally observed during snowmelt runoff. The TSS values for all four excursions were from 23 to 61 mg /l. This strict aquatic life standard (1.0 mg /1) was exceeded in over half of the pre- mining stream samples. Two samples from NPDESI7 exceeded the aquatic life chronic selenium standard, 4.6 ug /l, with values of 5 and 11.6 ug /1, potential dissolved (PD). The total recoverable (TR) value of 9.7 ug /1 noted on the table is not an excursion, as the standard is in the PD form. The acute standard, 18.4 ug /l, was not exceeded. See the following NPDES Effluent section for a discussion of these excursions. The sulfide data presented in Appendix E 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.mullalyengineering.com.au /images /product /file /Problem of Hydr ogen Sulphide in Sewers.pdf page 5, Table 1. No excursions of the 0.002 mg /l un- ionized sulfide standard occurred 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 to table standards found on this website, page 87: http://www.epa.gov/waterscience/criteria/ammonia/99u2date.pdf No ammonia excursions occurred this year. NPDES Effluent Criteria (Permit No. CO- 0000221). For NPDESI7, the two excursions of the selenium stream standard noted above were not NPDES permit limit excursions. The permit limit for this outfall for selenium 21