2015-03-31_REPORT - C1992081 - Laserfiche WebLink

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Well HGDAL3 is downgradient of the Loadout. It was drilled in 1993. It displays a slightly decresing TDS trend; however, the peak TDS value occurred in June 1997. Well HGDAL4 is upgradient of the Loadout. It was drilled in 2005. It displays an increasing TDS trend, with the peak TDS value occurring in May 2014. 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 /l, 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 3.620 mg /l. Downgradient Well HGDAL3 exceed the boron standard, 750 ug /1, with a value of 920 ug /l in September. According to the CDPHE, the 750 ug /l standard is set for sensitive crops (CDOH, Reg. 41, 2008), and that the limit otherwise is 5000 ug /1. None of these sensitive plant species are grown commercially in this area. In a letter dated June 5, 2008, Tom Kaldenbach of the CDRMS stated that "Groundwater points of compliance are unwarranted at the Hayden Gulch Loadout...". He further concluded that "... any leachate originating at the loadout would likely be of better quality than native groundwater in the Lewis Shale which has high concentrations of dissolved solids." This letter was provided in the 2008 AHR, Figure 3 (Appendix A). Monitoring conducted this year at the Loadout supports these conclusions. 5