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

RESULTS

WATER AVAILABILITY

1, Analysis of the recorded flow data for the Colorado River at the 'Cameo gaging station is
presented in Tab]e I. The average show that the average monthly amount of water
available under a junior right for diversion at the Webster Hill Reservoir site is estimated to
be approximately ]60,000 acre-feet. This figure was based on flow at the Cameo gage in
excess of 2,000 cfs during the irrigation season and in excess of 800 cfs during the winter
months.

2. Data in Tab]e 1further 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, ]979, ]980, 1985, and
1986) and the two years in which a release might be required (1982 and 1991) there would
have been sufficient water availab]e under a junior water right for diversion to storage in a
28,909 acre-feet reservoir at the Webster Hill site to permit the 20,000 acre-feet release for
recovery of the endangered species during late Mayor early June and to refill the reservoir
during late June, Ju]y and August to allow another 20,000 acre-feet release in the late
summer or early fall.

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

OPINION OF PROBABLE COST AND ECONOMIC FEASIBILITY

I. A conceptual opinion ofprobab]e cost for the 28, 909 acre-feet Webster Hill Reservoir is
approximately $76.4 million which would equate to approximately $2,600 per acre-foot of
storage or $146 per acre-foot of yield based on 40,000 acre-feet per year (see Tab]es 2
and 3). TIris $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) 1250 acres of rea] estate acquisition and (f) engineering and permitting.

2. An estimated $5.8 million in revenue would be produced annually from the 10 mw
hydropower installation (see Tab]e 4).

3. Netting out this $5.8 million in hydropower revenue from the amortized project capita]
costs would result in the cost of releases from the proposed reservoir being reduced to
approximately $6.40 per acre-foot from the $146 per acre-foot which did not include
hydropower revenue (see Tab]e 4).

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