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~~cmcx ~ <br />April 22, 2008 <br />Ms. Erica Crosby <br />Environmental Protection Specialist <br />Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, Colorado 80203 <br />~~~~~~ <br />APR 2 o zooo / <br />Division oi~ ibeclamatioii~ <br />dining and Safety <br />via Certified Mai1 7004 2890 0003 2043 0437 <br />Re: CEMEX Lyons Mine Permit M-1977-208 <br />Technical Revision No. 9, C-Pit Hydrogeologic Investigations <br />1st Quarter 2008 Monitoring Data <br />Dear Ms. Crosby: <br />This letter transmits surface water and groundwater data from sampling the C-Pit pond and <br />related wells, in keeping with the requirements of Technical Revision No. 9 to Permit No. <br />M-1977-208. <br />On March 11, 2008, CEMEX sampled the water in the pool at the north end of C-Pit, as <br />well as groundwater from monitoring well CEM-001 and alluvial well CEM-004. CEMEX <br />also continues to monitor the water elevation in C-Pit and in monitoring well CEM-001, <br />and measure the depth to water in compliance well CEM-005 located approximately 2,700 <br />feet southeast of C-Pit along Hygiene Road. Refer to the text, figures, and appendices of <br />the C-Pit Ilydrogeologic Investigations report (Brown and Caldwell, August 31, 2007) for site <br />details, well construction, and related information. <br />Analytical Data <br />C-Pit pond water and groundwater samples were analyzed for pH (field measurement), <br />dissolved selenium, dissolved thallium, chloride, sulfate, and dissolved solids. The table <br />below summarizes the results, and the analytical laboratory reports are enclosed with this <br />letter as an attachment. <br />As you can see, the selenium concentration in the C-Pit pool has lowered considerably from <br />the previous 500+ µg/L level down to 67 µg/L, and the pH remains below 9 su (standard <br />units), compared with previous levels as high as 12.5 su. This is presumably due to <br />attenuation by the backfill material that was placed in C-Pit during the spring and early <br />summer of last year. <br />Lyons Plant <br />P.O. Box 529, Lyons, CO 80540. USA, (303) 823-2100, Fax (303) 832-2199 <br />K:\EHS\Enviro\Compliance Forms and Submittals\DMRS C Pit\quarterty reports\YOBD1\CEMEX Transmittal 1st QTR 2008 Analytical Data.doc <br />