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STATE OF COLORADO <br />DIVISION OF RECLAMATION, MINING AND SAFETY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 C O L O R A D O <br />D I V I S I O N OF <br />Phone: (303) 866-3567 RECLAMATION <br />FAX: (303) 832-8106 MINING <br /> <br />July 27, 2010 SAFETY <br /> <br />Mr. John Cochran Bill Ritter, Jr. <br />Governor <br />Manager Environmental Hydrology <br /> Mike King <br />Peabody Investments Corporation Executive Director <br />3001 West Shamrell Boulevard, Suite 110 Loretta E. Pineda <br />Flagstaff, AZ 86001 Director <br />Re: Peabody Sage Creek Mine (C-2009-087) <br />Isotopic dating of ground water report (your letter of July 9, 2010) <br />Dear Mr. Cochran: <br />The Division of Reclamation, Mining and Safety has reviewed the above-referenced <br />letter and report in which you request that an additional baseline Wadge overburden well <br />not be required for a potential expansion of underground mine workings northwest of the <br />currently approved mine plan. <br />A hydraulic barrier is not needed to explain the difference in age between ground water <br />in deeper confined conditions (>1.15 million years) and in the near-surface outcrop area <br />(65 years). The age difference probably results from shallow ground water not reaching <br />the deeper areas because shallow ground water exits to the surface through springs before <br />flowing to the deeper areas where ground water is nearly stationary. The deeper ground <br />water is nearly stationary because it does not discharge to the surface. The greater <br />circulation near the surface results in the shallow ground water being much younger than <br />the deeper ground water, even though the two ground waters are hydraulically connected. <br />An additional baseline well is needed for adequately determining the attitude of the <br />potentiometric surface so that potential impacts from mine subsidence can be evaluated. <br />Please contact me if you have you would like to discuss this further. <br />Sincerely, <br /> <br />Tom Kaldenbach <br />Environmental Protection Specialist <br />cc (via email): Dan Hernandez, DRMS <br />Jason Musick, DRMS <br />Office of Office of <br />Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines