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In the years from 2006 to 2013, the water levels in M -12, M -13R, and M -14 have risen three (3) <br />to four (4) feet. Over this same period, the TDS concentration in M -14 became more variable and <br />appeared to trend higher in concentration. It is possible that this rise in water level may have rinsed <br />out existing naturally occurring salts (calcium, bicarbonate, sulfate, chloride etc.) from the <br />unsaturated zone above the water table, leading to an increase in concentrations of these salts. <br />3.3 Water Quality Results <br />Groundwater samples collected under this Response Plan were analyzed for the water quality <br />parameters outlined in TR -32. Samples were collected on a semi - monthly basis as outlined in the <br />Response Plan and have continued to be collected on a monthly basis since January, 2014. <br />Analytical results for samples collected under this Response Plan are shown in Table 1. During <br />the Response Plan, concentrations of the primary TDS analytes have been stable in well M -14 (see <br />Figure 4 and have not exhibited the variability shown in the years 2006 to 2013. <br />4.0 DATA ASSESSMENT <br />Total dissolved solids (TDS) is not an individual analyte but rather a term used to describe the <br />inorganic salts and small amounts of organic matter present in solution in water. The principal <br />constituents of TDS are usually calcium, magnesium, .sodium, and potassium cations and <br />carbonate, bicarbonate, chloride, sulfate, and nitrate anions. In assessing the TDS levels in <br />groundwater well M -14, these inorganic salts were evaluated in addition to TDS in order to assess <br />the correctness of the data and potential sources which may be contributing to TDS. <br />4.1 Analytical Correctness <br />Laboratory analytical data received have been reviewed for compliance with the laboratory <br />analytical method accuracy and precision criteria and were found to have met the data quality <br />objectives for this program. Additionally, as shown in Sections 4.1.1 — 4.1.3, the data have been <br />assessed for'analytical correctness in order to establish that the target analyte list is suitable for <br />evaluating the TDS concentrations. <br />4.1.1 Laboratory TDS Quality Control <br />Precision measures the reproducibility of the sampling and analytical methodology. Laboratory <br />and field precision is defined as the relative percent difference (RPD) between duplicate sample <br />TR -32 M -14 TDS Response Plan Report AES, Inc. <br />Battle Mountain Resources — San Luis, CO 5 January 2015 (Update) <br />