2022-06-02_HYDROLOGY - M1977344 - Laserfiche WebLink

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2022 Groundwater Monitoring Report www.arcadis.com 2022 Holcim FINAL GWMR 05132022 7  Potassium to Sodium Ratio: As shown in Table 2 and on Figure 3, the potassium to sodium ratio in all monitoring wells continues to be generally less than 0.10, indicating that there is no 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 and have remained stable in recent years (Figure 4). The concentrations of TDS in MW-12 and MW-13 are generally stable. 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 have remained stable in recent years. Concentrations are generally stable in MW-12 and MW-13, and though sulfate concentrations at MW-13 exceeded the NPL in 2022, the exceedance was not by more than 10 percent.  Manganese: Manganese concentrations in MW-7, MW-12, and MW-13 have decreased over time and have stabilized in the last 7 to 8 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. For this reason, TSS was added to the list of analytes in 2021. Analytical results are included in Figure 7 and the correlation between Total Iron and TSS is evident.  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 2022 sampling event (Table 2 and Figures 3, 4, 5, 6, and 8) remain generally higher than the wells installed downgradient of the CKD.