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fJEX <br />VMr. Michael Cunningham <br />Environmental Protection Specialist <br />Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, Colorado 80203 <br />April 20, 2012 <br />Via Certified Mail <br />Return Receipt Requested <br />7011 0470 0002 0359 3989 <br />Re: CEMEX Lyons Mine Permit 11977 -208 <br />Technical Revision No. 11, C -Pit Hydrogeologic Investigations <br />A st Quarter 2012 Monitoring Data <br />Dear Mr. Cunningham: <br />This letter transmits surface water and groundwater data associated with the sampling of cement <br />kiln dust disposal area (C -Pit) ponded water and monitoring wells 001 and 004 for the first <br />quarter of 2012. For your convenience, data from the last four quarters are included in Table 1 <br />as an attachment. The samples taken were sent to an independent lab and analyzed for pH, <br />chloride, sulfate, dissolved solids, dissolved selenium and dissolved thallium (Table 1). A field <br />pH was taken at the time of collection; this value is reported rather than the laboratory value due <br />to potential hold time changes that occur in pH values. <br />The analytical results from the monitoring well CEM -004 sample collected on March 8, 2012 <br />were anomalously high for nearly all parameters, including sulfate and chloride which exceeded <br />the target level concentrations. CEMEX immediately initiated additional sampling of the <br />groundwater in this well and evaluated other potential problems. Two additional samples were <br />collected on March 27, 2012 and April 4, 2012. The analytical data from the subsequent <br />sampling was much lower and consistent with historical concentrations of analytes seen in this <br />well. CEMEX could not identify any other potential source of error and the sample collection <br />process was consistent with standard historical practices (e.g., a pump dedicated to this well was <br />used, sampling procedures were followed, etc.). Therefore, CEMEX believes the data obtained <br />from the sample collected on March 8, 2012 from CEM -004 well was an outlier and not <br />representative of the groundwater characteristics <br />If there are any questions regarding the above information or the attachments, please contact me <br />at (303) 823 -2115. <br />