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Ms. Erica Crosby <br />March 3Q, 2007 <br />Page 2 <br />What axe the sources of water entering C-Pit? <br />~y/ktat is the potential for raising [he level of groundwater in the area of C-Pit during <br />the filling process, and will mounding of that water result in discharge to the <br />ground surface between C-Pit and A-Pit? <br />CEMEX is required to submit a plan to characterize and address groundwater in <br />the C-Pit area. <br />Subsequent to the February 9 meeting, CEMEX notified the Division of its intent to Fill C- <br />Pitwith inert material. Equipment was mobilized and materials were stockpiled the week of <br />February 19, 2007, and preparations for the filling operations commenced the following <br />week. A contractor began actual filling into the pit March 9. The filling process is presently <br />ongoing. Once it is completed and the free water in C-Pit is no longer exposed, the shale <br />fill in the eastern portion of the pit will serve as- a foundation for future CKD disposal <br />operations, and thereby eliminate the direct placement of fresh CKD into water. The lower <br />portion of the existing CKD that has been disposed in the western half of C-Pit will likely <br />remain saturated under the current conditions. <br />This letter outlines the scope of the first phase of hydrogeological investigations at C-Pit to <br />address the Division's concerns, and is submitted as a proposed Technical Revision No. 8 <br />('I'R-8) to the Lyons Mine Permit M-1977-208. Site-specific hydxogeologic information <br />obtained in this initial phase will be used to design a C-Pit monitoring program to be <br />submitted to DRMS for approval. <br />CEMEX proposes a phased approach to an enhanced management of C-Pit. The original <br />reclamation plan included placing spoil material into C-Pit. Later revisions speufically listed <br />CKD as a portion of this material and C-Pit remains the permitted CKD disposal site. <br />Should the results of the upcoming monitoring suggest an altemate location or disposal <br />method for CKD would be more appropriate, CEMEX will work with the DRMS and <br />other regulatory agencies to locate and permit such a location. The phases of work include: <br />1. Phase I -eliminate risk to wildlife via inert fill consistent with the <br />tedamation plan. During this phase, CEMEX commits to adding only <br />inert material, daily observation and identification of any seeps and/ or <br />springs, and notification to the DRMS should unexpected results occur. <br />2. Phase II - Conduct a hydrologic study, to include identifying the sources <br />of water (potential inflows into C-Pit), install a new compliance well into <br />the Fort Hays, and confirm the lack of connection to the St. Vrain <br />Alluvium. During this period CEMEX commits to continuing all existing <br />monitoring and additional monitoring as requested by DRMS. <br />3. Phase III -Use the results of Phase II to develop a corrective action plan <br />for any source water inflows, to develop an enhanced monitoring plan, and <br />work with additional regulatory agencies to identify alternate disposal <br />techniques that do not incorporate water. The results of Phase III will be <br />presented as a separate technical revision. <br />-0594686.doc <br />