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INTRODUCTION This report summarizes construction observation results for the on-site and laboratory quality assurance testing conducted during the construction of the Heit Pit slurry wall. Information contained within this report was collected as part of the construction related engineering services that were provided by Deere and Ault Consultants Inc. (D&A) throughout the slurry wall construction. The slurry wall was constructed by Hall-Irwin Construction under a contract with SW Meadows, LLC. Upon completion of the mining operations, the site will be used as a water storage reservoir. Construction of the Heit slurry wall began in early April 2007 and was completed in mid-June 2007. The construction consisted of lining a proposed gravel pit with approximately 6,566 feet of soil- bentonite slurry wall. The goal of the slurry wall liner is to minimize hydraulic interaction between the proposed gravel pit and the surrounding alluvium. The reduction in hydraulic interaction aids mining efficiency in two ways: 1) by reducing dewatering requirements during mining operations, and 2) by reducing draw down effects on any neighboring water wells. Upon completion of the mining activities, the final goal of the slurry wall construction is to provide a primary low permeability liner for a below grade water storage reservoir. The slurry wall was constructed using adesign/build approach. The scope of D&A's work during construction included on-site quality control and observation of the slurry wall construction. Hall- Irwin Construction supplied the labor, equipment, and materials to construct the slurry wall. PROJECT DESCRIPTION The project site is located near Fort Lupton, Colorado, and is bound by Weld County Road 25 on the east, Weld County Road 20 1/4 on the west. The site is more particularly described as being located in Section 13, Township 2 South, Range 67 West of the 6th Principal Meridian, Weld County, Colorado, as shown on the original construction plan set (Appendix C). Prior to slurry wall construction activities, the site was occupied and farmed by the Heit family. The house and associated structures, located in the center of the site, were removed before construction began. The ground surface of the site is relatively flat. The fields surrounding the house had not been farmed in some time. The project area is located approximately 20 miles east of the eastern flank of the Rocky Mountain Front Range. Regional geologic mapping of the area (Trimble, 1979)1 indicates the near surface bedrock at the site is the Upper Laramie Formation. The Upper Laramie Formation is described as being comprised of claystone, siltstone, and conglomerate with the claystone and siltstone partly altered to montmerillonitic clay. Bedrock at the site is overlain by alluvium mapped as the Piney Creek and Post-Piney Creek Alluvium. Trimble, D. and Machette, M., United States Geological Survey, Geolo ig c Map of the Greater Front Range Area Front Range Urban Corridor, Colorado. 1979 - 1 - September 2007 Heit Construction Report L•