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July 17, 2013 <br />Subject: Engineering Design, Proposed <br />Retaining Wall, RPEE Haul Road 2 <br />Switchback, West Elk Mine, Gunnison <br />County, Colorado <br />IR.77,411 iM11911M <br />Mr. Mike Peacock <br />Mountain Coal Company, L.L.C. <br />5174 Highway 133 <br />Somerset, Colorado 81434 <br />Dear Mr. Peacock, <br />This report presents engineering design for the proposed retaining wall to be constructed <br />for the RPEE Haul Road 2 Project located at the West Elk Mine in Gunnison County, <br />Colorado. This report presents the engineering design and drawings for the proposed <br />construction. <br />The retaining wall design is based on the following documents: <br />(1) Project Site Plan, PDF document, and AutoCAD drawings prepared by Mountain <br />Coal Company, dated June 17, 2013. <br />(2) Draft copies of soil borings SB -01 and SB -02 prepared by Barr Engineering <br />Company, dated June 6 and 7, 2013. <br />(3) Laboratory direct shear, index property, and unconfined compressive strength test <br />results by Lambert and Associates, dated between June 13 and July 16, 2013. <br />Proposed Construction and Design Assumptions <br />Based on the provided project documents and discussions with the Client, the proposed <br />project will consist of the construction of a single- tiered retaining wall. Based on the <br />proposed site grading near the retaining wall, we estimate that approximately 1,802 <br />square feet in face area will be constructed. We understand that the proposed wall will <br />be constructed utilizing Redi -Rock wet cast block units, Miragrid geogrid reinforcement, <br />import granular backfill, and gravel drainage aggregate. <br />Anticipated Subsurface Conditions <br />Limited geotechnical information was available at the time of this report preparation. <br />We do not anticipate that groundwater will be encountered during retaining wall <br />construction. <br />it-1 it-11 lip \ <br />ENGINEERING CONSULTRNTS INC. <br />101A Airpark Dr., Unit 9, PO Box 464, Gypsum, C081637 Phone (970) 524 -0720 Fax (970) 524 -0721 www.gmundeng.com <br />Office Locations: Englewood . Commerce City . Loveland . Granby . Gypsum . Grand Junction . Casper, WY <br />