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July 27, 2011 <br />File No. 111025 -000 <br />Hall -Irwin Corporation <br />301 Centennial Drive <br />Milliken, Colorado 80543 <br />Attention: Ed Lafferty <br />Dear Ed: <br />A DIVISION OF BRIERLEY ASSOCIATES, LLC <br />Engineering Solutions from the Ground Down <br />Subject: Design Report <br />Soil - Bentonite Slurry Wall <br />Geisert Gravel Pit <br />Weld County, Colorado <br />Lyman Henn is pleased to present this design report for the subject project. This report was conducted in <br />accordance with our contract dated June 8, 2001. <br />This report summarizes the subsurface explorations and conditions encountered along the slurry wall alignment <br />and provides specifications for the design elements of the slurry wall, slurry wall protection, and site <br />reclamation. Our scope of work did not include additional engineering services which may be required to use <br />the lined gravel pit at a water storage reservoir. Some of these additional engineering services include: <br />• Preparing an Office of the State Engineer Dam Construction Permit (Only required if the proposed reservoir <br />will store water above the natural ground surface; <br />• Preparing the design for reservoir hydraulic facilities (Inlet and Outlet structures); <br />• Performing an evaluation of the proposed mine reclamation slopes to determine if they can function as <br />permanent reservoir side slopes, particularly during rapid drawdown reservoir operations; <br />• Providing a topographic survey of the final reservoir configuration and use this survey to provide a stage - <br />storage curve for as- constructed reservoir capacity; <br />• Performing an evaluation of groundwater impacts (mounding or shadowing) caused by the slurry wall. <br />• Perform DRMS permitting services; and <br />• Perform an evaluation of the proposed gravel mine slopes and recommend safe setbacks and slope angles to <br />protect the slurry wall. <br />Lyman Henn can provide a proposal for these services upon request. <br />110 16"' Street, Suite 700 — Denver, CO 80202 -5202 — Tel: 303.534.1100 — Fax: 303.534.1777 — www.lymanhenn.com <br />Geotechnical, Tunneling and Construction Services <br />