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DEERE & AULT <br /> October 11, 2016 <br /> Ms. Lynn Mayer Shults <br /> L.G. Everist, Inc. <br /> 7321 East 88th Ave., Suite 200 <br /> Henderson, Colorado 80640 <br /> Re: Carbon Valley Gravel Mine Slope Stability Analysis; <br /> D&A Job No.CG-0201.029.00 <br /> Dear Ms. Mayer Shults: <br /> This letter presents Deere& Ault Consultants' (D&A) engineering analysis for the amended <br /> Carbon Valley Gravel Mine. The amended Carbon Valley Gravel Mine is located approximately <br /> 4.5 miles north of Firestone, Colorado, south of Weld County Road (WCR)26 and west of WCR <br /> 13 (Colorado Blvd). More specifically, the site is located in the Northwest Quarter of the <br /> Northwest Quarter of Section 6, Township 2 North, Range 67 West of the 6th P.M. in Weld <br /> County. A vicinity map of the area is shown on Figure 1. L.G. Everist, Inc. is in the process of <br /> evaluating the potential for the development of a gravel mine on the property. <br /> OVERVIEW <br /> L.G. Everist is developing permits required to open the mining cell with Environment, Inc. As <br /> part of the permitting process Environment, Inc asked D&A to perform slope stability analyses <br /> of the proposed mine slopes and proposed reclaimed slopes. The site is currently a cultivate field <br /> as shown on Figure 1. <br /> ANALYSIS <br /> D&A performed a slope stability analysis for the each of the four cross sections(Sections A-D) <br /> shown on Figure 1 using a mined highwall configuration. The highwall was assumed to be <br /> mined at a slope of 1:1 (horizontal to vertical). The distance to the nearest site feature, (i.e. <br /> property line, fence line, utility, etc.)is shown on each figure. Material properties for the <br /> existing geologic profile were assumed based on our professional experience with similar <br /> projects in the region. Each cross section was analyzed by the computer software Slope AV. The <br /> software performs calculations to develop thousands of failure circles between two user defined <br /> entry and exit sections, shown as red bars on the Figures 1-4. The ten failure circles with the <br /> lowest factors of safety are shown on each figure. The lowest factor of safety is called out by a <br /> red dot with a number and the correlating failure circle is a thick black line. The minimum <br /> factors of safety for the four mining slope cross sections ranged between 1.20 and 1.26. A <br /> temporary mine highwall with a factor of safety greater than 1.0 is considered stable. None of <br /> the sections analyzed came within 30 feet of affecting the nearest site feature. <br /> 600 S.Airport Road,Building A,Suite 205 <br /> Longmont,CO 90503 <br /> Phone: 303-651-1468 9 Fax: 303-651-1469 <br />