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<br />Review of the TDS regression plots indicates that NPDES 001 exhibits a <br />decreasing TDS trend. There is not enough TDS data for NPDES 002 to <br />indicate a trend. Upstream Site HGSDl displays an increasing TDS trend. <br />However, downstream site HGSD3 indicates a decreasing TDS trend. <br />Ground Water <br />Ground water quality reports for 2007 are presented in Appendix B. Data <br />provided includes a water quality report for this year, a listing of <br />water level data (and remarks) for the last ten years, and a listing of <br />a regression plot of historic TDS data. <br />This year's ground water quality was compared CDPHE ground water <br />agricultural use standards (Reg. 41, November 2004). Results of those <br />comparisons are presented in Table 4. That table indicates that the <br />downstream Well HGDAL3 exceeded the boron standard (750 ug/1) in October <br />with a value of 1000 ug/l. Both wells exceeded the manganese standard <br />(0.2 mg/1) in both May and October. <br />According to the CDPHE, the 750 ug/1 boron standard is set for sensitive <br />crops (CDPHE, Reg. 41, 2.004), and that the limit otherwise is 5000 ug/l. <br />None of these sensitive plant species are grown commercially in this <br />area. <br />It should also be noted that, while the CDPHE uses a manganese standard <br />of 0.2 mg/1, the EPA states that this standard is used to protect crops <br />grown in soils with a pH value lower than 6.0. In January 2008, CDPHE <br />revised their ground water agricultural standard to reflect this pH <br />qualifier. In soils with a higher pH (as are found in the HGT region), a <br />more appropriate standard would be 10 mg/1 (EPA. 1976. "Quality Criteria <br />for Water"). This year, none of the HGT wells displayed a manganese <br />value higher than 6.65 mg/l. <br />Finally, review of the TDS regression plots indicates decreasing trends <br />at both wells. <br />3