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Division of Aeclamation, <br />AX, M, ining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />November 21, 2014 <br />To: Tyler O'Donnell, Division of Reclamation, Mining & Safety <br />From: Peter Hays, Division of Reclamation, Mining & Safety <br />Re: Review of Slope Stability Analysis, Albert Frei & Sons Inc., Hatchery Pit, File No. M- <br />2014 -043 <br />The Division of Reclamation, Mining and Safety (Division) staff has reviewed the stability <br />analysis included with the Hatchery 112c permit application. The following list describes the <br />information used by the Division as presented in the permit application to evaluate slope <br />stability for the proposed pit: <br />• The Phase 1 and Phase 2 slurry walls will be completed prior to mining excavation <br />occurring. <br />• The site will be dewatered prior to mining extraction. <br />• Extraction of sand and gravel to occur at a 0.5H:1V slope, except the south slope in <br />Phase 1, which will be mined at 2H:1V. <br />• The excavation will be backfilled to original grade with inert material or a 3HAV slope <br />will be constructed with overburden material during final reclamation. <br />• Excavation will not occur within 200 feet of the City of Thornton Reservoir. <br />• The Phase 1 offset from the south side is 25 feet. <br />• The Phase 2 offset for the north, east and south slope is 25 feet with an additional <br />safety setback of 25 feet for a total offset of 50 feet from permit boundary to top of <br />slope. <br />• The extraction depth closest to any structure without a signed structure agreement <br />(communication line west of Monaco Street) is 42 feet. <br />• The average depth to bedrock is 15 -45 feet per the Mining Plan. <br />• No laboratory strength tests were performed on soils at the site. <br />• No borehole data was submitted with the permit application. <br />1. Please update the stability analysis to include surcharge loads from structures, roads <br />(Monaco Street), gas well facilities, topsoil stockpiles and any other appropriate loads. <br />,r T <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http: / /mining.state.co.us I ` <br />John W. Hickentooper, Governor I Mike King, Executive Director I Virginia Brannon, Director <br />