2010-03-22_REPORT - C1992081 - Laserfiche WebLink

Home Browse Search

0 • Ul The sulfide standard (0.002 mg/l, un-ionized) was exceeded at both surface water sites is June, with a value of 0.0027 mg/l observed at each site. Neither NPDES site was discharging at the time. The analytical method used detects both dissolved sulfides and acid-soluble metallic sulfides present in suspended matter. It is suspected that a large portion of the sulfides detected is of the latter type, which would bias the un-ionized results high. Any dissolved sulfides present in surface water should eventually oxidize to sulfates. Review of the TDS regression plots indicates that NPDESIH exhibits a decreasing TDS trend. There is not enough TDS data for NPDES2H to indicate a trend. Upstream Site HGSD1 displays a recently stable TDS trend. Likewise, downstream Site HGSD3 indicates a stable decreasing TDS trend. Ground Water Ground water quality reports for this year are presented in Appendix B. Data provided includes a water quality report for this year, sampling remarks and a listing of a regression plot of historic TDS data. A review of the TDS regression plots indicates stable trends at both wells. This year's ground water quality was compared against CDPHE ground water agricultural use standards (CDPHE, Reg. 41, 2008). Results of those comparisons are presented in Table 4. Both wells exceeded the manganese standard (0.2 mg/1) in both May and September. It should be noted that, while the CDPHE uses a manganese standard of 0.2 mg/1, the EPA states that this standard is used to protect crops grown in soils with a pH value lower than 6.0. In January 2008, CDPHE revised their ground water agricultural standard to reflect this pH qualifier. In soils with a higher pH (as are found in the HGT region), a more appropriate standard would be 10 mg/l (EPA. 1976. "Quality Criteria for Water"). This year, neither of the Loadout wells displayed a manganese value higher than 4.90 mg/1. 3