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0 Selenium (CDPHE irrigation) 1/1 <br />This summary indicates that only two CDPHE surface water agricultural <br />use standards were exceeded. The manganese standard was exceeded at <br />eight sites. However, as indicated in the recently revised CDPHE <br />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 Seneca <br />II region, a more appropriate (EPA) standard would be 10 mg/1. The <br />maximum manganese value for any surface water site observed this year <br />was 1.01 mg/1. Premining manganese values often exceeded the 0.2 mg/l <br />standard. <br />The selenium standard, 20 ug/l, was exceeded once at NPDESI3 with a <br />value of 27.7 ug/1, potentially dissolved (23.7 ug/l, total <br />recoverable). This is an irrigation standard. However, discharges from <br />this pond are not used for irrigation until it is diluted by Sage Creek. <br />Samples from Sage Creek did not exceed the standard. <br />Table 13 shows the CDPHE receiving stream standards f-or Sage and Grassy <br />Creeks (Yampa Segment 13e, Reg. 33, January 2009). These aquatic life <br />standards were based on the presence of fish in the lower portions of <br />the creeks. However, the upper portions that the Yoast Mine discharges <br />into have no fish present. Table 14 provides a comparison of those <br />standards to water quality data collected this year from NPDES and <br />stream sites in the Sage and Grassy Creek basins. Standards that were <br />exceeded are: <br />Parameter # of Sites / # of Excursions <br />Iron, Total Rec. 5/7 <br />Nitrite 1/1 <br />Selenium 1/4 <br />Sulfide 5/7 <br />The total recoverable iron standard (1.0 mg/1) was exceeded seven times <br />this year. Excursions were normally related to high suspended solids. <br />The one NPDES site excursion occurred during snowmelt runoff in April. <br />13