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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Woodward-Clyde Consultants <br /> <br />water annually. It is hoped that with rehabilitation of the spillway, Douglas Reservoir <br />may be able to provide up to 6,000 acre-feet. <br /> <br />Following a geotechnical field investigation, three alternatives for rehabilitating Douglas <br />Dam embankment were formulated and evaluated. One alternative would involve <br />construction of a cement-bentonite slurry wall cut-off along the axis of the dam. A <br />second alternative involved a clay blanket on the upstream slope of the embankment, <br />a cement-bentonite slurry wall cutoff at the upstream toe and construction of a buttress <br />on the downstream face of the dam. The third alternative, the selected option, involves <br />removal and replacement of the embankment above and to the outlet pipe and <br />construction of a soil-bentonite slurry wall cutoff at the upstream toe. For all three <br />alternatives, proposed spillway modifications involve filling in the existing spillway near <br />the left abutment and constructing a larger spillway near the right abutment of the dam. <br /> <br />The third alternative was selected for remediation of the seepage condition even though <br />it is the most rigorous of the three options. It allows for inspection of the outlet works, <br />construction of larger cut-off collars along the outlets and allows visible confirmation of <br />minimizing seepage along the outlet pipe. It also allows for the removal of anomalies <br />or deleterious material that may be in the embankment. <br /> <br />Cost estimates for the three options were formulated. An evaluation of the value of <br />Douglas Reservoir water indicated that any of the options would involve a cost which <br />would be much less than value of Douglas Reservoir water. A financial evaluation of <br />possible payment programs indicates that it would be feasible for Windsor Reservoir and <br />Canal Company to repay a 50% of construction costs loan from CWCB by making <br />assessments to its shareholders. <br /> <br />An estimated annual value of Douglas Reservoir water at $545 per acre-foot compares <br />well with the total project cost of about $235 per acre-foot or about average $6 per acre- <br />foot per year over a 40 year loan period. The cost of purchasing water from the <br />Colorado-Big Thompson would be about $1,400 to $1,500 per acre-foot per year (1990 <br />prices). <br /> <br />22539GIDOUGLAS.DAM 12-17-90/REPORTS3 <br /> <br />2 <br />