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analyses. The laboratory duplicate samples were performed to measure the precision of the analytical method and the RPD was calculated using the following equation: RPD = I (COncsample- COncDuplicate)I /((COncsample+ COncDuplicate) 12) * 100 The RPD for TDS was less than four (4) percent for all analyses which meets the data objectives for this program and no sample results were qualified based on laboratory duplicate QC results. Table 3 shows the TDS laboratory duplicates analyzed during the Response Plan. 4.1.2 Cation and Anion Balancing The sum of the cations and anions, expressed as milliequivalents per liter (meq/L), should be balanced because all waters are electrochemically neutral. This percentage difference can be calculated using the following equation: % Difference = ( Sumcatio ns- SUMAnions ) /(Sumcations +SumAnions) * 100 The calculated cation and anion balance from measured concentrations are shown in Table 4. The acceptance criteria under this Response Plan for the percent difference of the cations and anions is ± 5%. Based upon this acceptance criteria the measured percent differences are generally acceptable and indicate that the target analytes reflect the predominant constituents composing the TDS in monitoring well M -14. 4.1.3 Calculated TDS The correctness of the measured TDS value was verified by using the following formula: TDS = 0.61 * Alkalinity (as CaCO3) + Na + K + Ca + Mg + Cl + SO4 + Si02 + NO3 + F The measured TDS concentration would be higher than the calculated TDS if significant contributors were not be included in the calculation. A generally accepted ratio of measured TDS to calculated TDS should be less than 20 percent, otherwise the selected constituents for analysis may not accurately reflect the measured TDS. TR -32 M -14 TDS Response Plan Report AES, Inc. Battle Mountain Resources — San Luis, CO 6 January 2015 (Update)