WSP04151

• File Number: 8276.120
• Description: Grand Valley Unit-Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 5/23/1986
• Title: Final Environmental Impact Statement: Grand Valley Unit Stage Two Development
• Water Supply Pro - Doc Type: EIS

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SUMMARY (Continued)

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Alternatives

Two viable alternatives (A and B) plus a no-action alternative for
Stage Two development were considered. Alternatives A and B met the
criteria of four tests (completeness, effectiveness, efficiency, and
acceptability) used to identify viable plans that would meet the goals
of the salinity control program and Bureau of Reclamation and Department
of the Interior guidelines. From these alternatives, alternative B was
selected as the recommended plan of development.

During the planning process, a number of other salinity reduction
concepts and alternatives were studied but were dropped from further con-
sideration because they failed to pass one or more of the tests. These
alternatives included the concept of reducing salinity by combining
existing canal systems into fewer and more efficient facilities, the
concept of installing barrier cutoff walls along canal embankments, and
the addition of nine canal lining increments to alternatives A and B.
Options for combining systems were dropped from consideration because of
concerns of the water users about potential administrative and water
right problems and potential problems related to additional government
involvement. The concept of installing barrier cutoff walls was dropped
because the technique was unproven and its effectiveness in reducing
canal seepage was questionable. The additional increments to alterna-
tives A and B were dropped because of their relatively poor cost effec-
tiveness.

Recommended plan (alternative B)

The recommended plan would entail membrane lining three reaches of
the Government Highline Canal and replacing existing open earth laterals
with buried pipe laterals.

The canal improvements would consist of membrane lining approxi-
mately 38 miles of the 47-mile section of the Government Highline Canal
from Palisade to the canal's terminus, 6 miles northwest of Mack.l! Be-
cause of its small capacity, the last mile of the canal would be placed
in pipe. One segment of the canal was recently concrete lined under
Stage One. A mile-long siphon under East Salt Creek would not be re-
placed. The membrane lining would be 20-mil polyvinyl chloride, covered
with 14 to 19 inches of earth and gravel for all canal capacities.
Maj or existing structures along the canal, including siphons, flumes,
and bridges, would be subjected to a structural and hydraulic evaluation
and would be replaced if necessary. All turnout structures would be
replaced, and several new wasteway and centerline check structures would

1/ The first 6 miles of the canal from the Grand Valley Diversion
Dam to Palisade were excluded because the canal traverses the Mesa Verde
Formation, a much less saline formation than the Mancos Formation; be-
cause of the large capacity of the canal, it would be too expensive to
line.

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