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does not include the units of concentration (mg /l or ug /1) for each <br />parameter. The units used for each parameter are the same as those <br />listed on the Surface Water Parameter List (Table 1) and are also the <br />same as those used in the water quality reports. The frequency column on <br />Table 3 indicates, in this order: uncensored, that is, the number of <br />exceedances above the Method Detection Limit (MDL) / the number of <br />exceedances between the MDL and the Practical Quantitation Level (PQL) / <br />censored, that is, the number of sample values below the MDL but the MDL <br />was higher than the standard / the total number of samples. Below is a <br />summary of standards that were exceeded. <br />For both stream sites HGSD1 and HGSD3, the total recoverable iron <br />standard (1.0 mg /1) was exceeded in September with values of 1.08 and <br />1.01 mg /l. Neither NPDES outfall was discharging at the time. <br />The sulfide values provided in Table 3 differ from the values reported <br />in Appendix B. The sulfide data presented in Appendix B are the total of <br />both the ionized (S - ) and un- ionized (H forms of hydrogen sulfide. <br />The un- ionized form is the potentially toxic form, and is what the CDPHE <br />water quality standard is based upon. A procedure for calculating the <br />un- ionized form may be found on the website: <br />http: / /www.mullalyengineering.com.au /images /product /file /Problem of Hydr <br />ogen Sulphide in Sewers.pdf page 5, Table 1. The results of those <br />calculations are presented in Table 3 of this AHR. This year, no sulfide <br />excursions occurred. <br />The chronic selenium standard (4.6 ug /1) was exceeded in June at both <br />stream sites HGSD1 and HGSD3, with a values of 10.4 and 15.0 ug /l. The <br />acute standard (18.4 ug /1) was not exceeded. Irrigation return water <br />from the hay fields above upstream Site HGSD1 is most likely the cause <br />of these excursions. This entire area is composed of topsoils derived <br />from the Lewis Shale, which has naturally elevated concentrations of <br />selenium and dissolved solids. <br />HGT runs mercury tests with a Method Detection Limit (MDL) of 0.2 (or <br />sometimes 0.4) ug /l. All test values this year were less than the MDL. <br />3 <br />