2014-02-05_REPORT - C2009087 - Laserfiche WebLink

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classifications (livestock or irrigation) for surface water use evaluation. Parameter Manganese (CDPHE irrigation) # of Sites / # of Excursions 4/6 This summary indicates that only one of the CDPHE surface water agricultural use standards were exceeded. The manganese standard was exceeded at three 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 /1. All sites had manganese values less than 8 mg /1. It should also be noted that the site on Grassy Creek (SSG1) that is upstream of PSCM and Seneca II discharges has often experienced exceedances of the 0.2 mg /l standard. Table 12 shows the CDPHE receiving stream standards for Fish Creek (Yampa Segment 13b) . Table 13 provides a comparison of those standards to water quality data collected this year from NPDES4 and Site SSC10 (no flow at SSC10 in June of July) 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 1/2 Two samples from NPDES4 exceeded the chronic selenium standard of 4.6 ug /1, in April and May, with values of 4.9 and 6.4 ug /1, respectively. The potentially dissolved method is the method that is required for compliance. The dissolved and total recoverable selenium methods were run as a quality control check. The acute standard, 18.4 ug /1, was not exceeded. See the following NPDES effluent section for more details. In September 2003, the CDPHE resegmented Grassy Creek from Yampa Segment 12 to Segment 13e. Regulation 33 was further revised in December 2005 17