2021-01-05_HYDROLOGY - M1977344 - Laserfiche WebLink

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2020 GROUNDWATER MONITORING REPORT arcadis.com 7 discernible impact from the CKD disposal area. The K:Na ratios have stabilized or are declining in the last few years. • Total Dissolved Solids: TDS concentrations in MW-7 are generally decreasing through time (Figure 4). The concentrations of TDS and sulfate are generally stable in MW-12 and MW-13. All TDS concentrations remain below their respective NPLs. • Sulfate: Sulfate concentrations show a similar trend as TDS (Figure 5). MW-7 concentrations are generally decreasing through time and are generally stable in MW-12 and MW-13. All concentrations remain below their respective NPLs. • Manganese: Manganese concentrations in MW-7, MW-12, and MW-13 have decreased over time and have stabilized in the last 5 to 7 years (Figure 6). Manganese concentrations remain well below the respective NPLs at MW-7 and MW-13. • Total Iron: Total iron concentrations have exhibited considerable fluctuations at all three wells since monitoring for this parameter began in 2003 (Figure 7). Because total iron concentrations are strongly correlated to the amount of suspended solids contained in a groundwater sample, it is not surprising to observe these fluctuations in concentrations as small differences in how a sample was collected could impact the suspended solids concentration in that sample. • Dissolved Iron: Dissolved iron has stabilized at all three wells (Figure 8) and concentrations in MW-13 have remained below the DRMS issued NPL since 2009. • The concentrations of analytes found in monitoring well MW-12, which is considered the background well, from the March 2020 sampling event (Table 2 and Figures 3, 4, 5, 6, and 8) remain generally higher than the wells installed downgradient of the CKD. As previously mentioned, the total iron concentrations (Figure 7) have been relatively unstable in all three wells over the years, though the average concentration is highest at MW-12.