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1 <br /> 2018 GROUNDWATER MONITORING REPORT <br /> discernible impact from the CKD disposal area. The K:Na ratios have stabilized or are declining <br /> in the last few years. <br /> • Total Dissolved Solids:TDS concentrations in MW-7 are generally decreasing through time <br /> (Figure 4).The concentrations of TDS and sulfate are generally stable in MW-12 and MW-13. All <br /> TDS concentrations remain below their respective NPLs. <br /> • Sulfate: Sulfate concentrations show a similar trend as TDS (Figure 5). MW-7 concentrations are ' <br /> generally decreasing through time and are generally stable in MW-12 and MW-13. All <br /> concentrations remain below their respective NPLs. <br /> • Manganese: Manganese concentrations in MW-7, MW-12, and MW-13 have decreased over <br /> time and have stabilized in the last 3 to 5 years(Figure 6). Manganese concentrations remain <br /> well below the respective NPLs at MW-7 and MW-13. <br /> • Total Iron: Total iron concentrations have exhibited considerable fluctuations at all three wells ' <br /> since monitoring for this parameter began in 2003(Figure 7). Concentrations in MW-7 have <br /> decreased in the last two years and was less than 10% above the DRMS issued NPL in 2018. <br /> Because total iron concentrations are strongly correlated to the amount of suspended solids , <br /> contained in a groundwater sample, it is not surprising to observe these fluctuations in <br /> concentrations as small differences in how a sample was collected could impact the suspended <br /> solids concentration in that sample. <br /> • Dissolved Iron: Dissolved iron has stabilized at all three wells(Figure 8)and concentrations in <br /> MW-13 have remained below the DRMS issued NPL since 2009. <br /> • The concentrations of analytes found in monitoring well MW-12,which is considered the ' <br /> background well,from the March 2018 sampling event(Table 2 and Figures 3,4,5,6,and 8) <br /> remain generally higher than the wells installed downgradient of the CKD. As previously <br /> mentioned, the total iron concentrations(Figure 7) have been relatively unstable in all three wells <br /> over the years, though the average concentration is highest at MW-12. <br /> r <br />