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C 'MN6N'PYM16B ~ COw. CONPIANY A Cyprus Amax Company Twentymile Coal Corporation 29515 Routt County Road # 27 Oak Creek, Colorado 80467 970-879-3800 March 5, 1997 Larry Kline Office of Surface Mining 1999 Broadway Street, Suire 3320 Denver, Colorado 80202-5733 RE: Mine Plan Modification -Windy Gap Process for TR 97-28 Permit No. C-82-056 Dear Mr. Kline: T+ven[ymile Coal Company, through the PR-3 review and approval process, provided moneys for the above referenced process based upon a maximum production of 8,000,000 tons per year. This estimate will be based upon a maximum annual production of 10,000,000 tons per year. Although the amount that Twentymile will be required to submit will be based upon the additional 2,000,000 ton per year that can be mined once the technical revision is approved. Likewise, the water depletion estimate will be based upon the 2,000,000 ton increment due to the fact that the prior estimate was based on 8,000,000 tons per pear. • MINING CONSUMPTION The same sources of wafer identified in the prior estimate will be used at the operation. These include the existing deep well completed in the Trout Crcek Sandstone, spoil water pumped from a backfilled surface mine pit adjacent tot the operation and a storage pond, and underground seepage to the mine from the Wadge Overburden, which includes the Wadge Coal Seam. No alluvial pumpage or surface water diversions are proposed for mine use. In order to estimate water usage with the additional tonnage a production increase factor of 25%+vas applied to the estimates provided previously. Based upon the 25°l° increase in production the mine +vill use 4.29 ac-ft of wafer for this activity, which is an increase of 0.86 ac-ft per year. A limited amount of water t will come out on the coal 'll a remainder will remain underground. Additional bathhouse realer will w`~'~ be extracted from the Trout Creek Sandstone, and it is estimated that this usage will be 10.3 ac-ft. Likewise, the equipment washing has been increased by 25% resulting in an increase of 0.35 ac-ft per year. The surface road watering requirements are increased by 25% resulting in an increase of 0.1 ac-ft. VENTILATION CONSUMPTION No changes are anticipated in this requirement as the area is not increasing only the rate at which mining occurs. COAL PROCESSING CONSUMPTION It is planned to run the coal prep plant 12 months per year which results in increasing water consumption associated with this process by 124.3 ac-ft per year. The new annual requirement for this process is 213. I ac-ft per year.