WSP09974

• File Number: 8240.200.43.H.2
• Description: Grand Valley/Orchard Mesa -
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/13/1988
• Title: Draft - Proposed Solution to the Orchard Mesa Check Problem
• Water Supply Pro - Doc Type: Publication

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IV. COST ESTIMATES

Initial suggestions for system improvements to
compensate for sustained operation of the "check" structure
and bypass channel were made by the OMID staff and were
reviewed by representatives of the Colorado River Water
Conservation District, Colorado Water Conservation Board, and
U.S. Bureau of Reclamation. The Grand Junction Projects
Office of the Bureau prepared appraisal-level cost estimates
for the following features (See Figure 3):

- An auxiliary pumping plant, located adjacent to the
forebay of the existing plant, housing four electric
pumps. Two pumps are sized to lift 12 cfs 41 feet to
Orchard Mesa Canal '1 (low lift units) and two pumps
lift 10 cfs 123 feet to Orchard Mesa Canal '2 (high
lift units). ~he pumping duration is assumed to be
60 days per year and power will be purchased at
prevailing rates.

- The existing earth bypass channel, located parallel
to and east of the Colorado River, conveys water from
the tailrace at the south to the river at the north
when the existing radial gate check in the tailrace
is closed. The channel is about 1520 feet long and
has an average depth of cut of about 13 feet. The
prism will be restored to the original shape which
had a bottom width of 20 feet and a 1:1 side slope.
Channel discharge was assumed to be 650 cfs. Costs
of relocating Public Service Company's 13.2 kv
transmission line are included in the estimate.

- An earth dike, 370 feet long with a maximum height of
11 feet, will be constructed along the east bank of
the river at the north end of the bypass channel.
The dike will have a top width of 20 feet, riprap on
the river side, and will be fitted with a radial gate
structure to hold out the river.

Tables 3 and 4 present detailed cost estimates for the
described improvements. Table 5 contains annualized cost
information, including operation, maintenance, and replacement
costs associated with the project.

The Bureau points out that there is very little
information available about performance of the OMID hydraulic
pumps under varying tailwater elevations, and that small
variations in performance under different "check" operations
can have major impacts on the pumping rates required from the

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