PROJ02037

• Contract/PO #: PO 060000000018
• Contractor Name: Orchard Mesa Irrigation District
• Contract Type: Grant
• Water District: 0
• Loan Projects - Doc Type: Feasibility Study

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3

2

TASK 1 RESULTS
ENLARGEMENT STUDY

ORCHARD MESA POWER CANAL

2.1 Costs of increasing power canal capacity to 860 cfs

The total cost of increasing the capacity of the Orchard Mesa Power Canal was
determined by breaking into sections the entire Colorado River to Government Highline
Canal to Orchard Mesa Power Canal to Colorado River conveyance system. In order for
the system to operate at an increased capacity, every section of the system must be
capable of handling the increased flow rates. The overall conveyance system was
broken down into 14 parts. These parts were analyzed separately and estimated costs
were attached to each part based upon required improvements. A description of the 14
different sections and the required improvements for each section follows (note that the
stationing is approximate only):

Section 1 - Grand Valley Diversion Dam and Government Highline Canal above the
Colorado River Siphon. This portion of the project was designed to handle a flow rate of
1,675 cfs. Under current conditions, this canal must convey 730 cfs to the Grand Valley
Water Users Association (GVWUA), 800 cfs to the Orchard Mesa Power Canal, 80 cfs to
Palisade, and 40 cfs to Mesa County, or a total of 1,650 cfs. In order to deliver 860 cfs to
the Orchard Mesa Power Canal, the total capacity of the Government Highline Canal
would need to be increased by 35 cfs, to 1,710 cfs. For the purposes of this study, it has
been assumed that the canal can safely convey this additional flow.

Section 2 - Colorado River Siphon. The existing Colorado River Siphon is designed to
handle a flow rate of 800 cfs. In order to increase the capacity by 60 cfs to 860 cfs, the
inlet side of the siphon would need to have an increase in water-surface elevation of
1-1.5 ft, which could be achieved by placing additional fill and concrete around the inlet
works.

Section 3 - Flume Section 6+97 to 50+00. The existing flume is designed to handle a
flow rate of 812 cfs. During field observations, the flume was observed flowing at
approximately 800 cfs. At this flow rate, the flume was operating with 0.5 ft to 1.5 ft of
channel freeboard. In order to convey 860 cfs, the top of the concrete elevation of this
flume would need to be raised by approximately 1.0 ft.

2616-R1

Orchard Mesa Irrigation District

Water Management Consultants