2021-05-06_HYDROLOGY - M1977344 - Laserfiche WebLink

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G:\COMMON\Holcim\25510\05 Correspondence\response to DRMS TR 10 review of Na letter\sueker revision 20141118\2014 1119 Response to TR 10 review letter .docx Mr. Timothy A. Cazier November 19, 2014 Page: 2/6 ARCADIS Response: As presented below, multiple lines of evidence support the conclusion that increasing concentrations of sodium in groundwater samples collected at MW -7 are not associated with leachate from the CKD landfill. We have further evaluated the effect of depth to water in monitoring well MW -7 (see Figure 1 for location) to water quality in that well by preparing concentration versus depth to groundwater graphs for sulfate and potassium, two of the other constituents analyzed as part of the Groundwater Monitoring Plan (GMP) for the site. These graphs are presented in Figure 2 along with a sodium concentration versus depth to groundwater graph. The graphs demonstrate that while sodium concentration increase with increasing depth to groundwater, sulfate and sodium concentrations are inversely related to depth to groundwater. The correlation between and sulfate and potassium concentrations and depth to water is not as strong when compared to sodium after 2010, as indicated by the two observed “spikes” in concentration (Figure 2), particularly for sulfate. However, for both potassium and sulfate, when depth to groundwater decreases, constituent concentrations increase. All three constituents are present in the CKD (see Table 1), and potassium and sulfate are present in the CKD at much higher concentrations than sodium (see discussion below) and all three constituents are highly leachable.. It follows that if the observed increases in sodium concentrations were associated with the CKD landfill, then corresponding increases in sulfate and potassium should be observed. The historical data for these two constituents do not exhibit this pattern. In addition to the observed relationship between depth to water and sodium, sulfate, and potassium concentrations, there are additional lines of evidence that the increase in sodium concentrations are not related to releases from the CKD landfill. The basis for this position is that the concentrations of sodium in the groundwater should reflect its concentration in the CKD as well as its concentration relative to other constituents in the CKD. We present below both compositional and leach test data from the CKD to demonstrate that sodium concentrations in groundwater at MW -7 are not attributable to leaching from CKD. CKD chemistry indicates high concentrations of potassium and chloride relative to sodium. Table 1 is a summary of compositional CKD analyses from the Portland plant for 2014 for sodium, potassium, and chloride. Sodium and potassium analyses are presented as oxides of these parameters. The data indicate that the average potassium concentration is greater than sodium by more than a factor of 10 (K:Na > 10). Chloride concentrations in the CKD exceed sodium concentrations in the CKD by nearly factor of 20 (Cl:Na >20). Table 2 summarizes compositional potassium