2016-04-22_REPORT - C2009087 - Laserfiche WebLink

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This summary indicates that only one of the CDPHE surface water agricultural use standards was exceeded. The manganese standard was exceeded at four sites. However, as indicated in the recently revised CDPHE Regulation 31, the standard of 0.2 mg/l applies to plants grown in acidic (<6.0 pH) soils. In alkaline soils, as are found in the PSCM region, a more appropriate (EPA) standard would be 10 mg/l. All sites had manganese values less than 1 mg/1. It should also be noted that the site on Grassy Creek (SSG1) that is upstream of PSCM discharges has often experienced exceedances of the 0.2 mg/l standard. Table 12 in Appendix A shows the CDPHE receiving stream standards for Fish Creek (Yampa Segment 13g). This new segment came into effect December 31, 2014. Table 13 in Appendix A provides a comparison of those standards to water quality data collected this year from NPDES4 and Site SSC10 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 NPDES4 discharge into. Standards that were exceeded are: Parameter # of Sites / # of Excursions Selenium 1/1 One sample from Site SSC10 exceeded the chronic selenium standard of 4.6 ug/l with a value of 5.6 ug/l in May 2015. However, there is a temporary modification (expires December 31, 2018) of the selenium standard as "current conditions". Therefore, this excursion is not considered to be a standard exceedance. Table 14 in Appendix A shows the CDPHE receiving stream standards for Upper Grassy Creek (Yampa Segment 13). This new segment came into effect December 31, 2014. Table 15 in Appendix A provides a comparison of those standards to water quality data collected this year from NPDES and stream sites in the Grassy Creek basin. Standards that were exceeded are: 20