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AVCOLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />Date: January 28, 2015 <br />To: Eric Scott, Division of Reclamation, Mining & Safety <br />From: Peter Hays, Division of Reclamation, Mining & Safety <br />Re: Second Review of Slope Stability Analysis, Martin Marietta Materials, Three Bells <br />Mine, File No. M- 1979 -191 <br />The Division of Reclamation, Mining and Safety (Division) staff has reviewed the stability <br />analysis included with the Three Bells Mine permit amendment (AM -01) application and the <br />adequacy response received January 27, 2015. <br />The following list describes the information used by the Division as presented in the permit <br />amendment application to evaluate slope stability for the mine. <br />• Geotechnical boring data was provided by the Applicant. <br />• A compacted clay liner will be installed as part of final reclamation to create reservoirs. <br />• The depth of overburden and pit run material vary in depths depending on the Mining <br />Phase and location. <br />• The depth to bedrock varies from 8 to 19 feet below the existing ground surface. <br />• The depth to groundwater varies from 2 to 9 feet below the existing ground surface. <br />• The proposed mine highwalls will be mined vertically and vary in height from 9 to 17 <br />feet. <br />• Laboratory strength tests were not performed on the site soils. <br />• Residual soil strength parameters were used for the upper 2.5 feet of weathered <br />bedrock. <br />• The site will be dewatered prior to mining extraction. <br />• The closest structure to the mine excavation limits in the power line pole owned by <br />Poudre Valley REA at 29 feet from the excavation limit. <br />Using Clover Technology's Galena v6.1 slope stability software, the Division conducted further <br />analysis of the two cross - sections for the Three Bells Mine. Specific comments and <br />requirements for each of the cross sections are provided below. <br />CO�Od <br />NQ 90 <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http: / /mining. state. co. us I 1 <br />John W. Hickentooper, Governor I Mike King, Executive Director I Virginia Brannon, Director * 187 <br />