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~ ~ TRgrPSR ~t~z~~ inc. III IIIIIIIIIIIIIIII December 13, 1985 EXPRESS MAIL Mr. James McArdle Colorado Mined Land Reclamation Division 423 Centennial Bldg. 1313 Sherman St. Denver CO 80203 Dear Jim: Enclosed is the hydrologic investigation performed gravel operation. The analysis was performed by Mr engineering, Casper, Wyoming. ~~~ ~E ~C~g~ "' -'`.~ on Trapper Mine's sand and . George Hoffman of Hydro- In summary, the analysis indicates that the greatest affect on the adjacent cottonwood trees will occur during the mining of area 3. The drawdown during the period of maximum pumping should be less than one foot (.74 ft, page 4-1 of the report). However, to prevent the mining of areas 5 and 6 from impacting the cottonwood trees, a change in mining sequence is proposed. Mining areas labeled 5 and 6 on Exhibit C will be reversed. This change will maintain a dike of land between areas 1, 2 and 3 and areas 4, 5 and 6 for almost the entire life of the project. The area between mining areas 1 and new 6 would be mined out at Che end of mining. Thus, little or no drawdown impacts would be caused to the cotton- woods once mining enters areas 4, 5 and 6. A revised Exhibit C will be sent shortly showing the change in mining sequence. Page 3-1 of the hydrologic report states "Dewatering is no[ expected to last more than thirty days in any one year." In actual practice, the sentence should read "Dewatering is not expected to last more than thirty days during any active period in any one year." This is not a change that would affect the hydrologic analysis since the analysis was calculated based on pumping during late August-early September, the period of low flows in the Yampa River. Also the 30-day period would be worst case. Trapper may wish to mine at other times and the sentence as drafted may lead the Division to the false concluson that mining would occur only thirty days per year. cont. P.O. Box 187 Craig, Colorado 81626 (303) 824-4401