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Pecelveo <br />CC-t1 ax v <br />JUL 2 6 2010 <br />Division of Rtbton, <br />Mining 8 ?pZJuly 15, 2010 f <br />Mr. Allen Sorenson Via Certified Mail 7007 2680 0001 6296 0262 <br />Environmental Protection Specialist Return Receipt Requested <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 />,?XqGchnical_ R_ e_ visiocL10 C-Pit Hydrogeologic Investigations <br />2nd Quarter 2010 Monitoring Data <br />Dear Mr. Sorenson: <br />In keeping with the requirements of Technical Revision No. 9 to Permit No. M-1977-208, this <br />letter transmits surface water and groundwater data from sampling the C-Pit pond and related <br />wells for the second quarter 2010. In TR9, we agreed to conduct five consecutive quarters of <br />sampling, beginning in fourth quarter 2007 and a re-evaluation of monitoring parameters at that <br />time. <br />There are two potential formations of concern in the area; the Fort Hayes and the St. Wain <br />Alluvium. Monitoring in the Fort Hayes was conducted at compliance well CEM-005. As <br />CEM-005, the compliance well located in the Fort Hayes collapsed, there is not a monitoring <br />point associated with that formation. Previous groundwater modeling and subsequent monitoring <br />demonstrated that there is not impact or likely interaction with the Fort Hayes formation. Thus, <br />were are proposing no more monitoring in the Fort Hayes formation. <br />Continued monitoring and observations indicate that no additional seeps or springs down the <br />gradient of C-Pit are occurring. As agreed upon in TR-9, we will continue to monitor for the <br />presence of seeps or springs. <br />On June 3, 2010, CEMEX personnel sampled the water in the pool at the north end of C-Pit, and <br />alluvial well, CEM-004. CEMEX also monitored the water elevation in C-Pit and several <br />piezometers. Please refer to the text, figures, and appendices of the C-Pit Hydrogeologic <br />Investigations report (Brown and Caldwell, August 31, 2007) for site details, well construction, <br />and related historical information. <br />The C-Pit pond water and groundwater samples taken were analyzed for pH, chloride, sulfate, <br />dissolved solids, dissolved selenium and dissolved thallium. The most recent analytical <br />laboratory reports are enclosed with this letter as an attachment. Samples were analyzed