2005-07-12_REVISION - M2000016 (3)

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~~S ~FARGE / NORTH AMERICA AGGREGATES, CONCRETE & ASPHALT July 11, 2005 Mr. Gregg Squire Division of Minerals and Geology 1313 Sherman St., Rom 215 Denver, Colorado 80203 RECEII/ED JUL 12 2005 ~ Division ~f Minerals and Geology RE: Third Adequacy Review Response, Lafarge West, Inc. Riverbend Operation 112c Permit Amendment Ol, Permit No. M-2000-016 ~ Deaz Mr. Squire, i ~/~ Lafage received the third adequacy review from the Division of Minerals and Geology (Division) for the Riverbend Pit 112c Amendment O1, File Number M-2000-016. The following responses have been prepared to address the Division's concerns. For clazity, each of the Division's comments is quoted in italics and followed by Lafazge's response. Additional responses to the second adequacy review aze located at the end of this letter. Responses to Kathleen Sullivan Memo, Geotechnical Adequacv Review -June 23, 2005 Please explain the meaning of the last sentence on p. 2 of 5 in the "Ft. Lupton Pit Slope Stability Study" (Study) by Weiland, Inc., "It should be noted that minimum factors of safety were determined for each slope analyzed and in all cases, the proposed slope with assumed stratigraphy and soil characteristic parameters returned a value for FS of less than 1. Q indicating that the proposed slope would fail under the existing conditions. " Please see enclosed response prepared by Weiland, Inc. for clarification. 2. In the February 11, 2005 adequacy review, the Division requested drill hole records. The data provided contained borehole locations and overburden and sand and gravel thicknesses, but not ground water levels or information on soil characterization. Please provide well logs and completion diagrams so the Division may verify how the soil was classif ed and depths to ground water. Please see enclosed response prepared by Weiland, Inc. regading the soil classification and depths to ground water used in the Study. Responses to Kathleen Sullivan Memo, Geotechnical Adequacv Review -June 28, 2005 Pursuant to discussions regarding our meeting on Friday, June 25, 2005, I am providing the following list of drill hole numbers for which the Division requires well logs and/or completion diagrams to verify ground water levels utilized for the geotechnical slope stability analyses. LAFARGE NORTH AMERICA INC. -Lafarge Construction Materials 10170 Church Ranch Way, Suite 200, Westminster, Colorado 80021 Telephone: (303) 6574000 Facsimile: (303) 657-4037