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May 29, 2013 <br />//CC-MC-X <br />samples collected on March 6, 2013, April 10, 2013, and April 25, 2013 dropped to levels within <br />the target monitoring goals for chloride. Sulfate levels dropped below the target monitoring <br />goals in the April 25, 2013 groundwater sample. A summary of the data discussed is being <br />provided in Table 1 below: <br />Table 1: Summary of Chloride and Sulfate Detections in CEM -004 in Spring 2013 <br />y ., `004 <br />Parameter / Date <br />2/7/2013 <br />2/21/2013 <br />3/6/2013 4/10/2013 <br />4/25/2013 <br />H (On -site) (SU) <br />7.5 <br />- <br />7.4 7.0 <br />7.2 <br />Chloride (mg /1) <br />478 <br />554 <br />123 157 <br />27 <br />Sulfate (m 1) <br />1630 <br />1820 <br />458 542 <br />161 <br />Dissolved Solids (mg /1) <br />3478 <br />3830 <br />- 1260 <br />368 <br />Selenium, Dissolved (mg/L_ <br />0.0025 <br />10.0021 <br />- 0.0047 <br />- <br />Thallium, Dissolved (mg/1) <br /><0.0004 <br />1 <0.0004 <br />- <0.0004 <br />- <br />Review of Charge Balance with April 2013, Historical data, and Hydrogeology <br />On March 8, 2012, a similar spike was observed in the chloride and sulfate concentrations, but <br />these concentrations dropped below the monitoring goals by the end of the month (March 27, <br />2012). When CEMEX discovered the elevated levels of sulfate and chloride in February 2013, <br />it was decided that additional samples would be collected to assess whether a similar drop in <br />chloride and sulfate would occur as it did in 2012. When the sulfate remained higher than the <br />monitoring goals it was decided to analyze for cations and anions to obtain a geochemical <br />signature (fingerprint) for both the CEM -004 groundwater and the C -Pit water. Previous <br />analyses did not include all the principal cations and anions and focused only on the monitoring <br />parameters. <br />A cation/anion balance was conducted with the April 25, 2013 data for both the CEM -004 and <br />the C -Pit and plotted on Stiff Diagrams. This evaluation is shown in Table 2. Stiff Plots are <br />shown in Figure 1. As shown in Figure 1, there continues to be a distinctive difference in the <br />chemical signature between CEM -004 and C -Pit. This signature is consistent with the historical <br />characteristics of the water from these two different areas as seen in Figure 10 of the Technical <br />Revision No. 8. It is acknowledged however, that the data from CEM -004 collected in February <br />and March 2013 appears to be anomalous for chloride and sulfate and the stiff diagrams could <br />not be plotted for those data because only the monitoring parameters were analyzed. <br />2 <br />