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6.4 Chemistry of Calcium and Sodium <br />Based upon the ion - exchange process discussed in Section 6.2, a significant increase in the sodium <br />concentration would be expected in the event of mixing of LTF and well M -14 waters, but this is <br />not observed. As shown in Figure 10, well M -14 has shown no increasing trend in sodium. In <br />addition, the relative concentrations of calcium and sodium in the Tailing Pond and Collection <br />Ditch samples differ significantly from those found in well M -14. In summary, the lack of <br />increasing concentrations of sodium in well M -14 indicates that leakage from the LTF is not the <br />cause of historic (approximately 2002 — 2010) increasing calcium in well M -14. <br />7.0 RESPONSE PLAN SUMMARY <br />The objective of the Response Plan sampling was to determine if TDS concentrations could be <br />stabilized through low -flow sampling and if so, analyze the Response Plan data and other historical <br />records to identify if the variability of results and concentrations of TDS in well M -14 could be <br />attributed to any identifiable site conditions. The average percent` relative standard deviation <br />( %RSD) of all TDS samples collected during the Response Plan was 1.39 percent and shows that <br />the measured TDS concentrations have been very stable throughout the entire Response Plan. The <br />TDS results correlated very well between field measured electrical conductivity, sample <br />duplicates, cation and anion balances, and the calculated TDS. This indicates that the data <br />collected were complete and of such quality that they could be used in further analysis of potential <br />site conditions which may be impacting the TDS concentrations in well M -14. <br />Based upon the geologic and hydrogeologic conditions existing at well M -14, the theoretical solid <br />surface and ion - exchange reactions, and the analytical data reviewed from the LTF monitoring <br />system, we conclude that leakage from the LTF is not causing the variability and increased levels <br />of TDS and calcium found in well M -14. Importantly, the lack of a significant increase in the <br />sodium and sulfate concentrations and the absence of other analytes clearly shows that there has <br />been no detectable mixing of LTF and well M -14 waters. <br />The variability and concentration increases of TDS in well M -14 over time are directly related to <br />the increase in calcium and alkalinity over this period. Review of historical records and the data <br />TR -32 M -14 TDS Response Plan Report AES, Inc. <br />Battle Mountain Resources — San Luis, CO 13 January 2015 (Update) <br />