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The iron standard is 1.0 ug/l. Site SSSPG2 exceeded this standard in <br />2018 with a concentration of 1.8 ug/1. <br />The selenium standard of 4.6 ug/l was exceeded at three sites in 2018; <br />NPDES4, SSSPGI and SSSPG2. Lewis Shale soils have contributed to the <br />high selenium values observed in many of the streams in this area. <br />However, there is a temporary modification (expires December 31, 2018) <br />of the selenium standard as "current conditions". Therefore, this <br />excursion is not considered a standard exceedance. <br />Table 14 in Appendix A shows the CDPHE receiving stream standards for <br />Upper Grassy Creek (Yampa Segment 13). This new segment came into effect <br />December 31, 2014. Table 15 in Appendix A provides a comparison of <br />those standards to water quality data collected this year from NPDES and <br />stream sites in the Grassy Creek basin. Standards that were exceeded <br />are: <br />Parameter # of Sites / # of Excursions <br />Iron, Total Rec. 3/5 <br />Selenium 1/1 <br />The chronic copper MDL is 50 ug/l. The test value at NPDES2 in October <br />this year was less than the MDL. The chronic copper standard is 29 <br />ug/l. <br />The iron standard is 1.0 ug/l. Sites SSG1, SSLGS and YSGFS exceeded <br />this standard in 2018. In general, iron excursions are the result of <br />high suspended solids. There is a temporary modification (expires <br />December 31, 2018) of the iron standard as "current conditions". <br />Therefore, this excursion is not considered a standard exceedance. <br />The mercury MDL is 0.20 ug/l. All test values this year were less than <br />the MDL. The mercury standard is 0.01 ug/1. <br />The selenium standard of 4.6 ug/l was exceeded at SSSPG4 with a <br />concentration of 11.8 ug/l in 2018. The high selenium values at these <br />110 <br />