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Slope Stability Analysis -Haldorson Sand and Gravel Mine <br />This report describes the slope stability analysis (SSA) for the proposed Haldorson and <br />Sons Sand and Gravel Mine located on Spring Creek Mesa near Montrose, Colorado. <br />The SSA was completed as required by DMG Rule 6.4.19(b) to support mining within the <br />200-ft setback. Existing structures within 200 ft of the Haldorson property mining limits <br />include an overhead utility, Chipeta Water District water line, fire hydrant, fiber optic <br />cable, and two residential buildings on the north side of LaSalle Road. <br />Background Data <br />Soil borings indicate that topsoil and overburden depths on the property range from two <br />feet to seven feet in depth, averaging five feet in depth. The surface material is <br />underlain by sand and gravel extending to bedrock at a depth of 32 feet in Phase five at <br />the south property boundary, and to a depth of greater than 60 feet on the northerly part <br />of the property. The 60-foot borings did not encounter bedrock. Below the sand and <br />gravel layer is Mancos Shale formation bedrock. <br />The USDA NRCS (formerly Soil Conservation Service) soil survey for the area indicates <br />that three soil types overlie the majority of the Haldorson property: <br />• Menoken - Chacra Clay Loam <br />• Mesa Gravelly Clay Loam Shale Substratum <br />• Mesa Clay Loam <br />These surficial materials on the site comprise an upper layer of clay loam and gravelly <br />clay loam extending from four inches to 60 inches in depth. Small areas of Mesa <br />Gravelly Clay Loam and Chipeta - Persayo Range Complex are also present, but will <br />not be affected by the proposed mining activities. <br />Soil testing was not completed for the Haldorson property, so no site-specific soil <br />properties are known. Soil properties were assumed based on research and knowledge <br />of similar materials properties. Conservative values have been assigned to the materials <br />and are presented in the table below. <br />\\Bgserver\public\Projects By Client\Haldorson 8 Sons\03023-Haldorson Mine\03023_Slope Stability writeup_RMM.doc <br />