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# of Sites / # of Excursions <br />Manganese (CDPHE irrigation) 9/15 <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 nine sites. However, as indicated in the recently revised <br />CDPHE Regulation 31, the standard of 0.2 mg/l, applies to plants grown <br />in acidic (<6.0 pH) soils. In alkaline soils, as are found in the Seneca <br />II -W region, a more appropriate (EPA) standard would be 10 mg/l. The <br />maximum manganese value for any surface water site observed this year <br />was 5.27 mg/1 at site WSSPG-1. Pre -mining manganese values often <br />exceeded the 0.2 mg/l standard. <br />Table 12 shows the CDPHE receiving stream standards for upper Dry Creek <br />(Yampa Segment 13d) and Table 14 shows the Sage Creek (Yampa Segment <br />13e). Sage Creek was resegmented by the CDPHE in 2003. Regulation 33 was <br />further revised in 2005, 2008 and 2015. These standards were based on <br />the presence of fish in the lower portions of the creeks. However, the <br />upper portions that Seneca II -W discharges into have no fish present. <br />Tables 13 (Yampa Segment 13d) and 15 (Yampa Segment 13e) provide a <br />comparison of those standards to water quality data collected this year <br />from NPDES and stream sites in those basins. Standards that were <br />exceeded are: <br />Parameter # of Sites / # of Excursions <br />Ammonia, Nitrogen N 8/9 <br />Iron, Total Recoverable (TR) 8/14 <br />Manganese, Dissolved 1/1 <br />Nitrite, Nitrogen N 1/1 <br />The aquatic life ammonia standard is dependent on pH and temperature. <br />The detection limit for ammonia is 0.05 mg/l. All values above detection <br />limit are compared to table standards found on this website, page 87: <br />http://www.epa.gov/waterscience/criteria/ammonia/99update.pdf <br />23 <br />