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Mr. Mark Johnson <br /> March 17, 2017 <br /> Page 3 <br /> ► Section A-A': This section considers WCR 13/N. County Road 1, and Xcel Energy's gas line and facility <br /> 100'west of the mine highwall. A high phreatic surface was included to model the maximum water <br /> surface. A surcharge of 400 psf was included to model the live load of the road. <br /> ► Section B-B': This section considers WCR 13/N. County Road 1 and utilities. A high phreatic surface <br /> was included to model the maximum water surface. A surcharge of 400 psf was included to model the live <br /> load of the road. <br /> ► Section C-C': This section considers Highway 3921 WCR 68 and utilities. A high phreatic surface was <br /> included to model the maximum water surface. A surcharge of 400 psf was included to model the live load <br /> of the road <br /> ► Section D-D': This section considers the overhead power line along the eastern boundary of the site. A <br /> high phreatic surface was included to model the maximum water surface. A surcharge of 200 psf was <br /> included to model the live load from the access road and dead load from the overhead power line. <br /> The material index and engineering strengths assumed in this slope stability report are discussed below. <br /> MATERIAL PROPERTIES <br /> Overburden <br /> The index properties for the insitu clay overburden were based on field testing data and on our engineering <br /> judgment; the following parameters have been used to model the overburden. <br /> Dry Unit Moist Unit Saturated Unit Cohesion C'psf Friction Angle V° <br /> Weight(pco Weight(pco Weight c <br /> 103 114 126 50 29 <br /> Alluvial Sand and Gravel <br /> The sand and gravel is generally medium-grained sand, medium dense, poorly to well graded, and generally clean. <br /> The deposit ranges from fine to coarse sand with some silt and occasional rounded to well rounded gravels less <br /> than two inches in diameter The alluvial sand and gravel has been modeled as follows: <br /> Dry Unit Weight Moist Unit Saturated Unit Cohesion C'psf Friction Angle m'° <br /> (Pco Weight(pco Weight c <br /> 119 129 130 0 35 <br /> Claystone Bedrock <br /> The proposed mine area is generally underlain by claystone bedrock. Claystone is generally a weak bedrock and is <br /> often prone to slope instability and the bedrock foundation strength is critical for the highwall stability. For the <br /> claystone bedrock, two potential strength conditions were considered. These strength conditions are referred to as: <br /> 1) peak strength, and 2)residual strength. <br /> Peak strength is the maximum shear strength the claystone bedrock exhibits. The shear strength is made up of <br /> both cohesion (diagenetic bonding)and internal friction. Under short-term conditions for unsheared claystone, peak <br /> strength governs behavior. If a sheared surface or sheared zone is present within claystone as a result of faulting, <br /> slippage between beds due to folding, past shrink-swell behavior, stress relief,or from a landslide, the cohesion <br /> along the sheared surface is reduced to zero, and the angle of internal friction is decreased, due to alignment of <br />