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~D <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />7373 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX: (303) 832-8706 <br />December 27, 2004 '~ <br />Mr. John Lohr <br />CEMEX <br />P.O. Box 529 <br />Lyons, CO 80540 <br />RE: CEMEX, Inc., Lyons Mine, Permit No. M-1977 208 <br />Recap of 12-17-04 Meeting <br />Dear Mr. Lohr, <br />COLORADO <br />DIVISION O E <br />MINEBRALS <br />GEOLOGY <br />REC LAMATION•M INING <br />SAFETY•SCIENCE <br />eill Owens <br />Governor <br />Russell George <br />Executive Direttor <br />Ronald W. Cattany <br />Division Director <br />NaMal Resource Trustee <br />CEMEX, INC. and the Division discussed a number of issues related to the C-Pit during the 12- <br />17-04 meeting. The Division has a few additional comments regarding the C-Pit that CEMEX <br />may wish to consider. <br />If you want to lower the Ph limit to 9, the Division suggests that it be lowered to pH 8.9 <br />since the standard is pH 9 or less. <br />2. If the goal is to dewater the pond so that there is no pool and the ability to pump below 4 <br />feet is related to some physical constraint, CEMEX should consider a sump pump. <br />3. In terms of bonding and final reclamation, how will the site be left so that no after <br />permit release pumping will be required to prevent ponding of water? And what is the <br />cost for that to happen? <br />4. With regard to grading needs for the post-mining land use, there maybe only limited <br />need to take significant precautions as long as the post mining land use is to be <br />rangeland. If the site is proposed to include the construction of structures, additional <br />precautions may be required. There is a multi-step azgument, starting with chemistry; <br />The active reagent in CICD is lime - CaO. Ca0 in contact with atmospheric C02 <br />produces CaC03, calcite, limestone and this can happen in a few days to weeks. C02 <br />can be expected to be present and available anywhere above the water table. The <br />reaction between Ca0 and C02 will produce CaC03. It usually will form a pulverulent <br />limestone - a calcium cazbonate mass that will crumble under minimal pressure. This <br />limestone will not react with water at the high rate that Ca0 (CKD) will react, so it will <br />not be able to release Se at the rate of CKD because the Se will be tied up in the calcite, <br />and the surface area of the limestone mass would be much smaller than that of the CKD. <br />Office of <br />Mined Land Reclamation <br />v <br />Office of <br />Active and Inactive Mines <br />Colorado <br />Geological Survey <br />