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2020 GROUNDWATER MONITORING REPORT <br />arcadis.com 8 <br />4 CONCLUSIONS AND RECOMMENDATIONS <br />Arcadis presents the following conclusions based on the information presented in this report: <br />• For the March 2020 groundwater sampling event, concentrations of all analytes measured in the two <br />downgradient wells, MW-7 and MW-13, were below the NPLs except for the total iron result for MW- <br />7. The concentration of total iron in monitoring well MW-7 was more than 10% over the NPL. <br />However, no other exceedances were observed and per the revised GMP, resampling of MW-7 is not <br />required. <br />• Because total iron concentrations are strongly correlated with the amount of suspended solids <br />contained in a groundwater sample, it is suggested that total suspended solids (TSS) analysis be <br />added to the groundwater sampling program. <br />• Concentrations of TDS and sulfate are generally decreasing in MW-7 and generally stable in MW-13. <br />• Generally stable or decreasing trends for manganese, dissolved iron, and potassium to sodium ratios <br />continue to be observed in wells MW-7 and MW-13. <br />• Groundwater flow is to the south and velocity is 0.3 foot to 2 feet per year, which is consistent with <br />historical data. In addition, groundwater elevations and interpreted flow direction are similar to <br />previous sample rounds. <br /> <br />Based on March 2020 sampling results that indicate there is no discernible impact from the CKD disposal <br />area and that only one parameter (total iron) exceeded its NPL, Arcadis recommends that groundwater <br />monitoring continue on an annual basis. Arcadis also recommends that TSS analysis be added to the <br />groundwater sampling program in 2021 to monitor the correlation of concentrations of suspended solids <br />and total iron. <br /> <br />