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//CC- mcx <br />Figure 2: C -Pit Stiff Plot — Average C -Pit Signature and 10 Percent Decrease in the <br />Average Signature. <br />Cakmm <br />Magnesium <br />Potassium <br />Sodium <br />C -Pit Cation -Anion Signature with 90% Concentration <br />a <br />I <br />legend <br />® . .r .. <br />Bicatbonale <br />Carbonate <br />Chbode <br />+ Sulfate <br />100 50 0 50 too <br />Table 2: Revised Triggers for Compliance Well CEM -005, based on the 90% of the <br />Average C -Pit Concentrations for Chloride and Sulfate. <br />Analyte /Parameter <br />Trigger Concentration <br />(mg/1) <br />pH <br />6.5 -8.5 <br />Chloride <br />1,053 <br />Sulfate <br />2,641 <br />Total Dissolved Solids <br />501- 10,000 or 1.25 times <br />background <br />Selenium <br />0.05 <br />Thallium <br />0.002 <br />As you are aware, CEMEX conducts compliance monitoring at well CEM -005 quarterly. In <br />addition, CEMEX conducts quarterly monitoring at two wells that are upgradient of CEM -005, <br />and downgradient of C -Pit: <br />• CEM -001 which is 144 feet deep and completed in an interval that monitors <br />groundwater in the Carlile -Fort Hays - Smokey Hills interface. <br />• CEM -004 is an alluvial well that is 23 feet deep. <br />CEMEX will continue to monitor CEM -004 and will compare chloride and sulfate data to the <br />proposed trigger levels. Using the modified triggers for chloride and sulfate proposed in Table <br />2, the monitoring program will be designed to effectively identify potential impacts on <br />groundwater quality from C -Pit. CEM -001 will continue to be monitored and reported without <br />required monitoring targets. <br />United States Operations <br />P 0 Box 529, Lyons, CO 80540, USA, Phone (303) 823 -2100, Fax (303) 823 -2199 <br />