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2021 Groundwater Monitoring Report <br />www.arcadis.com <br />2021 Holcim FINAL GWMR 7 <br /> Total Dissolved Solids: TDS concentrations in MW-7 are generally decreasing through time (Figure 4). The <br />concentrations of TDS in MW-12 and MW-13 are generally stable. All TDS concentrations remain below their <br />respective NPLs. <br /> Sulfate: Sulfate concentrations show a similar trend as TDS (Figure 5). MW-7 concentrations are generally <br />decreasing through time and are generally stable in MW-12 and MW-13. All concentrations remain below <br />their respective NPLs. <br /> Manganese: Manganese concentrations in MW-7, MW-12, and MW-13 have decreased over time and have <br />stabilized in the last 6 to 7 years (Figure 6). Manganese concentrations remain well below the respective <br />NPLs at MW-7 and MW-13. <br /> Total Iron: Total iron concentrations have exhibited considerable fluctuations at all three wells since <br />monitoring for this parameter began in 2003 (Figure 7). Because total iron concentrations are strongly <br />correlated to the amount of suspended solids contained in a groundwater sample, it is not surprising to <br />observe these fluctuations in concentrations as small differences in how a sample was collected could impact <br />the suspended solids concentration in that sample. TSS was added to the list of analytes in 2021 and future <br />analytical results will be monitored for correlations to total iron concentrations. <br /> Dissolved Iron: Dissolved iron has stabilized at all three wells (Figure 8) and concentrations in MW-13 have <br />remained below the DRMS issued NPL since 2009. <br /> The concentrations of analytes found in monitoring well MW-12, which is considered the background well, <br />from the March 2021 sampling event (Table 2 and Figures 3, 4, 5, 6, and 8) remain generally higher than the <br />wells installed downgradient of the CKD. <br /> <br />