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~ ;. ~L.AFARG E NORTH AMERICA /~ Construction Materials September 21, 2004 RE: Lafarge West, Inc., Application No. M-2003-091 Duckworth Pit, Adequacy~tesponse #3 Erica Crosby Division of Minerals and Geology 1313 Sherman St., Room 215 Denver, CO 80203 Dear Erica, RECEi~ SEP 2 7 2004 Division of Minerals & Geology Lafarge received the adequacy review from Division of Minerals and Geology (Division) for the Duckworth Pit New 112 Application, File Number M-2003-091. The following response has been prepared to address the Division's concern; previous Division comments are summarized in italics. The Division previously asked Lafarge to demonstrate topsoil piles stored on site would fie stable in their current configuration ifan adequate buffer distance was not established. Lafarge responded by changing the miningslope from O.Sh:ly to LSh:ly arrd stating that an angle of repose egual or less than 1.5:1 achieves a safety greater than 1. However, Lafarge did not provide a slope stability analysis to demonstrate that the angle of repose would achieve a static safety factor greater than I. Lafarge has not provided a mining offset distance from the toe of the topsoil pile to the edge of the pit, nor has Lafarge demonstrated that the pile will be stable at the edge of the L Sh: l v pit. Please address this issue prior to final approval of the Duckworth 112 Application. In addition, please explain how the highwalls will be reduced and reclaimed in areas where topsoil is stored. Following our September 20, 2004 telephone conversation, Lafarge understands the Division's primary concern to be execution of mining and reclamation activities while maintaining the 1.Sh:ly slope. The crest of the mining face will align with the designated mining limits as indicated in Exhibit C. The mining limits will be located using GPS surveying equipment and identified by staking. Using a minimum 1.Sh:ly slope, the toe will be calculated and also staked. Front-end loaders, dozers, or excavators will be used within the mine boundary to excavate the material according to the staked toe. Once the deposit has been removed, the same equipment will place overburden material back into the slope while operating on the pit floor. Once the overburden has been placed, the equipment will pull the topsoil piles down onto the slope. Lafarge has successfully used LAFARGE NORTH AMERICA INC. -Lafarge Construction Materials 1400 West 64'" Avenue, Denver, Colorado 80221 Telephone: (303) 657-4000 Facsimile: (303) 657-4037