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Peabody <br />• <br />Twentymile Coal <br />Apri13, 2007 <br />Mr. Cazl Johnston <br />Office of Surface Mining Reclamation and Enforcement <br />1900 Broadway -Suite 3320 <br />Denver, Colorado 80201 <br />(303) 844-1500 <br />Re: Twentymile Coal Company -Foidel Creek Mine (Permit C-82-056), Technical Revision TR07-59 <br />- Changes in Water Balance and Update of Windy Gap Analysis <br />Dear Mr. Johnston: <br />29575 Routt County Road 27 <br />Oak Creek, CO 80467 <br />970.879.3800 <br />Twentymile Coal Company (TCC) has applied for approval of applicable permits to construct and <br />operate a new Washplant, in order to maintain and enhance the quality of our coal product, consistent <br />with changes in geologic conditions and market demand. Projected increases in production to 12.0 <br />MM tons per yeaz (clean coal), and the addition of the new Washplant, will result in increases in <br />consumptive use and the addition of surface moisture to the washed coal. Given these anticipated <br />changes, with this submittal, TCC has updated the mine water balance and Windy Gap Analysis <br />accordingly. <br />The original Windy Gap Analysis for the Foidel Creek operations was completed in 1986, and the <br />required one-time mitigation payment was made, based on consumptive use under an 8.0 MM ton per <br />year production scenario. The Analysis was revised and updated in 1997, to reflect changes in <br />consumptive use associated with an increase in annual production to 10.0 MM tons. <br />Currently, the only surface water that TCC uses in its mining and related operations is a limited <br />amount of surface runoff/spoil spring discharge (approximately 163.6 acre-feet per year) from a large <br />on-site reservoir, previously constructed as a combination sedimentation structure and storage reservoir <br />in conjunction with historic surface mining activities in the area. The large majority of the water used <br />in ongoing operations comes from ground water sources, predominately mine inflows, with a small <br />amount coming from TCC's existing potable water well. It is not anticipated that these system inputs <br />will change significantly over the remaining life-of--mine. <br />TCC has an active ongoing mine water recycling program, where both mine and process water aze <br />recycled to underground storage reservoirs in sealed and abandoned underground mine workings for <br />reuse. As a result, little or no discharge to surface drainages occurs, consumptive use is limited to <br />surface moisture shipped with the coal product and evaporative losses, and any variance between <br />system inputs and losses translates into changes (plus or minus) in ground water storage, as indicated <br />• by the attached Table E51-25, Simplified Water Balance. <br />