WSP09467

• File Number: 8281.990
• Description: Colorado River Studies and Investigations -- Webster Hill Dam and Reservoir
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/2001
• Author: Brown and Caldwell
• Title: Technical Memo NO 4A: Analysis of Alternative 4 - New Storage Facility at Webster Hill Site - Mainstem Colorado River
• Water Supply Pro - Doc Type: Report/Study

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DRAFT

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t\:) EXECUTIVE SUMMARY
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......The purpose of Technical Memorandum 4A is to present the results fro~ further investigating the
Webster Hill reservoir site located on the mainstem of the Colorado River immediately
downstream from Rifle, Colorado, This further investigation focuses primarily on water
availability for diversion to storage under a junior storage right at the Webster Hill site and the
potential economic feasibility ofthis site for development as a storage reservoir.

The following findings, conclusions and recommendations are based on this analysis:

1. Analysis of the recorded flow data for the Colorado River at the Cameo gaging station is
presented in Table 1. These data indicate that approximately 160,000 acre-feet are
estimated to be available under a junior right for diversion at the Webster Hill Reservoir
site on an average monthly basis.

2, Data in Table 1 further indicate that for those six years of the 1975-1991 study period in
which the 20,000 acre-feet release would be required (1975, 1978, 1979, 1980, 1985, and
1986) and the two years in which a release might be required (1982 and 1991): (a) there
would be sufficient water available under a junior water right for diversion to storage in a
28,909 acre-feet reservoir at the Webster Hill site to allow the 20,000 acre-feet release for
recovery of the endangered species during late Mayor early June and (b) it would be
possible to refill the proposed reservoir during late June, July and August and to make
another 20,000 acre-feet release in the late summer or early fall.

3. A 200 cfs flow would be available for nm-of-the-river hydropower generation at the
Webster Hill Reservoir site in all months for the 1966-97 data set presented in Table 1.

4. A conceptual opinion of probable cost for the 28, 909 acre-feet Webster Hill Reservoir is
approximately $76.4 million, This total cost would equate to approximately $2,600 per
acre-foot of storage or $146 per acre-foot of yield based on an expected yield of 40,000
acre-feet per year (two 20,000 acre-feet releases), This $76.4 million total cost estimate
includes: (a) a 10 mw hydropower installation, (b) relocating the railroad, (c) 1-70 vertical
realignment, (d) gas well relocation, (e) 1,250 acres of real estate acquisition and (f)
engineering and permitting.

5. An estimated $5.8 million in revenue would be produced annually from the 10 mw
hydropower installation.

6. Netting out this $5.8 million in hydropower revenue from the amortized project capital
costs would result in the cost of releases from the proposed reservoir being reduced to
approximately $6.40 per acre-foot.

7. It is concluded that the Webster Hill site with hydropower generation is an economically
feasible alternative for supplying the 20,000 acre-feet releases required for the Recovery
Program, Before concluding that this alternative is feasible from an engineering

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