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ffcEmcEx <br />Mr. Michael Cunningham <br />Environmental Protection Specialist <br />Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, Colorado 80203 <br />Re: CEMEX Lyons Mine Permit M- 1977 -208 <br />Dear Mr. Cunningham: <br />April 25 2012 <br />Via FEDEX <br />799634479026 <br />1st Quarter 2013 Monitoring Data Sulfate & Chloride report <br />RECEIVED <br />APR 302013 <br />Division of Reclamation, <br />Mining & Safety <br />This letter summarizes information gathered in the first quarter of 2013 relating to the <br />Monitoring Well CEM -004 (23 feet below grade) which indicated that two monitoring <br />parameters, sulfate and chloride, were greater than the monitoring goals identified in Technical <br />Revision 11 (TR -11). As you may recall, CEMEX notified you of this information by phone on <br />February 22, 2013, two days after receiving the data from the laboratory. On February 26, 2013, <br />an e -mail was sent outlining additional monitoring that we planned to conduct. <br />Monitoring goals for CEM -004 chloride and sulfate are 250 mg /l. Initially, the data for samples <br />collected on February 7, 2013 were 478 mg /1 chloride and 1,630 mg /l sulfate. CEMEX <br />immediately requested the laboratory reanalyze the initial collected sample and we collected an <br />additional sampling of the groundwater in this well. The reanalysis of the February 7, 2013 <br />sample only showed minor differences. Additional samples were collected on February 21, <br />2013, March 6, 2013, and April 10, 2013. The samples collected on March 6, 2013 and April 10, <br />201 dropped to levels within the target monitoring goals for chloride. The sulfate remains high <br />but dropped significantly compared to the samples collected on 2/7/13 and 2/21/13. A summary <br />of the data is provided in the table below: <br />Parameter / Date <br />pH (On -site) (SU) <br />Chloride (mg/I) <br />Sulfate (mg/I) <br />Dissolved Solids (mg/I) <br />Selenium, Dissolved (mg /L <br />Thallium, Dissolved (mg/I) <br />2/7/2013 2/21/2013 3/6/2013 4/10/2013 <br />7.5 <br />478 <br />1630 <br />3478 <br />0.0025 <br /><0.0004 <br />554 <br />1820 <br />3830 <br />0.0021 <br /><0.0004 <br />7.4 <br />123 <br />458 <br />7.0 <br />157 <br />542 <br />1260 <br />0.0047 <br /><0.0004 <br />CEMEX will continue to sample the well on an increased basis until the sulfate numbers are <br />within the monitoring goals set forth. Additional samples have already been collected and sent <br />