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DEERE & AULT <br />February 13, 2006 <br />Mr. Dave Nettles, P.E. <br />State Engineer's Office <br />810 9th Street, Suite 200 <br />Greeley, Colorado 80631 <br />Re: Brannan Pit No. 29 South Cell Leak Test, United Water and Sanitation District; <br />D&A Job No. CG-0178.002.00 <br />Dear Mr. Nettles: <br />We have prepared this letter to outline our proposed procedure for conducting a 90-day leak test <br />for the south cell of the proposed Brannan #29 gravel pit reservoir. <br />BACKGROUND <br />6 <br />Brannan Pit #29 is an active gravel mine approximately five miles southwest of Brighton, <br />Colorado. The gravel mine is between Old Brighton Road on the west, U.S. Highway 85 on the <br />east, E-470 on the north, and 124th Avenue on the south. The site lies about one-quarter mile <br />east of the South Platte River, and the Fulton Ditch flows eastward near the south end of the pit. <br />United Water and Sanitation District proposes to develop the gravel mine for raw water storage. <br />In the fall and winter of 2003-2004, a soil-bentonite slurry wall was constructed around the entire <br />pit and an intermediate wall was constructed across the pit creating a separate north cell and <br />south cell. The slurry wall was designed by Tetra Tech RMC and constructed by Geocon, Inc. <br />An independent contractor hired by United Water and Sanitation District provided regular <br />Quality Control during the slurry wall construction and Tetra Tech RMC provided Quality <br />Assurance oversight. The slurry wall construction was completed in general conformance with <br />the plans and specifications. Detailed documentation of the Quality Control testing can be <br />provided if necessary. <br />Since the slurry wall construction was completed, the south cell has been partially dewatered. <br />The main gravel mining and processing takes place in the north cell. United Water and <br />Sanitation District wants to proceed with the leak test of the south cell. <br />Figure 1 (attached) is a plan showing the as-built alignment of the slurry wall around the south <br />cell, existing monitoring wells, the proposed pumping sumps, and other site details. <br />600 S. Airport Road, Building A, Suite 205 <br />Longmont, CO 80503 <br />Phone: 303-651-1468 Fax: 303-651-1469