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stream sites in the Grassy Creek basin. Standards that were exceeded <br />are: <br />Parameter <br />Copper, Pot. Diss. <br />Iron, Total Rec. <br />Mercury <br />Selenium <br /># of Sites / # of Excursions <br />1/1 <br />4/6 <br />8/8 <br />2/2 <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/1. <br />All iron excursions were the result of high suspended solids. There is <br />a temporary modification (expires December 31, 2018) of the iron <br />standard as "current conditions". Therefore, this excursion is not <br />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/l. <br />The selenium standard of 4.6 ug/l was exceeded at SSLGS with a <br />concentration of 5.9 ug/l in April. Site SSSPG4 also exhibited an <br />exceedance in June with a value of 7.20 ug/1. The high selenium values <br />at these sites in part come from Scotchman's Gulch, which is in contact <br />with Lewis Shale soils. Lewis Shale soils have contributed to the high <br />selenium values observed in many of the streams in this area. However, <br />there is a temporary modification (expires December 31, 2018) of the <br />selenium standard as "current conditions". Therefore, this excursion is <br />not considered a standard exceedance. <br />Table 16 in Appendix A shows the CDPHE receiving stream standards for <br />Lower Grassy Creek (Yampa Segment 13j). This new segment came into <br />effect December 31, 2014. Table 17 provides a comparison of those <br />standards to water quality data collected this year from NPDES and <br />18 <br />