WSP04996

• File Number: 8276.100
• Description: Grand Valley Unit - Colorado River Basin Salinity Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 8/1/1985
• Title: Summary Sheet -- Grand Valley Unit - Colorado River Basin Salinity Control Project
• Water Supply Pro - Doc Type: Project Overview

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s rAGE ONE

The definite plan report for the Stage One water
systems improvement program was published in March
1980. Preliminary environmental studies were
conducted on the unit, and a negative determination
of env i roomen tal impact for Stage One was made in
1978.

Stage One construction began in October 1980. It
covers approximately 10 percent of the unit area
and was designed to provide information to fully
analyze the effectiveness of the overall unit. As
part of the development, 6.8 miles of the Govern-
ment Highline Canal were concrete-lined and
cross-drainage facilities were constructed. In
addition, 13 open channel laterals were consoli-
dated into 12 pipe laterals and a moss and debris
removal structure was placed at the beginning of
the canal 1 ining. T~e Grand Valley field station
serves as construction headquarters for the overall
unit and is being used for operation and main-
tenance or for other project uses. Construction of
Stage One was essentially completed in April 1983
at a construction cost of $27,744,000. The
development resulted in a reduction in salt
loading to the Colorado River of about 19,900 tons
per year and a decrease in salinity at Imperial Dam
of about 1.8 mg/L, at a cost effectiveness of $93
per ton.

To assess the effects of Stage One improvements on
ground-water flows and quality, surface- and
ground-water inflows and outflows were monitored in
a hydrologically closed basin known as the Reed
Wash study area. Under the monitoring program,
water-level measurements and samples were taken
either monthly or continuously from observation
wells to provide data for evaluating the effects of
Stage One improvements on ground-water flows and
quality in tributary drains. Results from the
water-quality testing are being used to assess the
effectiveness of Stage One development in reducing
salt to the Colorado River. Wildlife resources are
also being monitored in the Stage One area to
determine the effects of Stage One improvements on
wildli fe resources.

STAGE TWO

Stage Two investigations, which began in November
1981, included reevaluating various alternatives
and analy~ing salinity control measures other than
lining, since nonlining options were minimally
studied before authorization.

Studies are continuing to determine the nature and
extent of salt loading to the Colorado River. Data
collection includes: 1) flow measurements and

Grand Valley Unit
August 1985
Page 2 of 2

samples from all major washes and drains and from
selected canals and laterals, 2) samples and water
level measurements from .:in extensive network of
wells (valleywide), and 3) water and salt budget
computations for the Grand Valley and for 17
subbasin areas within the valley.

The Stage Two plan coverf, the remaining canal and
lateral systems in the vall,~y exclusive of the Stage
One area (see map). Areas excluded from Stage Two,
in addition to Stage One, i':'1clude the Redlands area
and the Orchard Mesa Power Canal. The plan provides
for installing pipe laterals (private and Federal)
in the entire Stage Two ,s,rea and 1 ining the west
end, middle, and east end portions of the Government
Highl ine Canal. The west end portion of the canal
and laterals would be constructed first. Improve-
ment of the middle and east end portions of the
canal would be deferred until needed to meet goals
of the salinity control program. Collection of
technical and environmental preconstruction data is
continuing.

Wildlife habitat replacement measures were
authorized by Congress unde"[' Public Law 98-569.

Construction costs for Stage Two are estimated at
approximately $190,000,000, based on January 1984
appraisal-level prices. Implementing the plan would
result in a reduction in salt loading to the
Colorado River of about 143,500 tons per year and a
decrease in salinity at Imp,~rial dam of about 13.1
mg/L, at a cost effectiveness of $89 per ton.

TOTAL GRAND VALLEY UNIT STATISTICS

Construction costs for Stage One plus Stage Two are
estimated at $220,000,000, based on January 1984
appraisal-level prices. Implementing both plans
would result in a reduction in salt loading to the
Colorado River of about 163,400 tons annually and a
decrease in salinity at Impl~rial Dam of about 14.9
mg/t, ,at a cost effectiveness of $89 per ton.

REPORTS

Completion of the draft environmental
statement is scheduled for late 1985 and the
environmental impact statement for mid-1986.

impact
final

LOCAL INTEREST

The Grand Valley Salinity Coordinating Committee
meets regularly and is open to all persons and
agencies interested in attending. The purpose of
the cormnittee is to coordinate salinity studies in
the Grand Valley and to disseminate information to
the public.