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does not differentiate between livestock and irrigation uses in their <br />surface water agricultural standards, they have done so in their similar <br />ground water agricultural standards (see Table 5). For the sake of <br />discussion, PSCM chooses to use those ground water use standards <br />classifications (livestock or irrigation) for surface water use <br />evaluation. <br />Parameter # of Sites / # of Excursions <br />Manganese (CDPHE irrigation) 7/9 <br />This summary indicates that only one of the CDPHE surface water <br />agricultural use standards was exceeded. The manganese standard was <br />exceeded at seven sites. However, as indicated in the recently revised <br />CDPHE Regulation 31, the standard of 0.2 mg /l applies to plants grown in <br />acidic ( <6.0 pH) soils. In alkaline soils, as are found in the PSCM <br />region, a more appropriate (EPA) standard would be 10 mg /1. All sites <br />except SSSPG6 had manganese values less than 1 mg /1. It should also be <br />noted that the site on Grassy Creek (SSG1) that is upstream of PSCM and <br />Seneca II discharges has often experienced exceedances of the 0.2 mg /l <br />standard. <br />Table 12 shows the CDPHE receiving stream standards for Fish Creek <br />(Yampa Segment 13b). Table 13 provides a comparison of those standards <br />to water quality data collected this year from NPDES4 and Site SSC10 (no <br />flow at SSC10 in October) in the Fish Creek basin. The stream standards <br />for Fish Creek are based on aquatic life standards, even though there <br />are no fish present in the upper portion of the tributary that NPDES4 <br />discharge into. Standards that were exceeded are: <br />Parameter # of Sites / # of Excursions <br />Selenium 1/2 <br />Iron, Total Rec. 1/1 <br />Two samples from NPDES4 exceeded the chronic selenium standard of 4.6 <br />ug /1, in April and May, with values of 7.6 and 9.1 ug /1, respectively. <br />The potentially dissolved method is the method that is required for <br />17 <br />