WSP07690

• File Number: 8277.600.10
• Description: Big Sandy River Unit - Colorado River Salinity Control Program
• State: WY
• Basin: Colorado Mainstem
• Date: 9/1/1987
• Title: Final Environmental Impact Statement for the Big Sandy River Unit
• Water Supply Pro - Doc Type: EIS

I

SUMMARY

The Selected Plan proposes the installation of the following structures
on 15,700 acres of irrigated land in the Big Sandy River Unit to reduce
salinity in the Colorado River Basin. (See Figure S-l, Location Map.)

Distribution Pipeline and Risers
Motor, Pumps, and Valves
Low Pressure Sprinkler Irrigation Systems
Semi-Automated and Automated Border Irrigation Systems
Irrigation-Regulating Reservoirs and Wasteway System
Voluntary Replacement of Fish and Wildlife Habitat Values

Economic and environmental analyses are based on the estimated
15,700 acres of participation. Actual acreage will vary depending on
individual participation in the program. Participation will be
voluntary and implemented through long-term contracts administered by
the ASCS. Technical assistance for salinity control and conservation
planning, implementation of planned practices, assistance to realize
irrigation water management objectives, and installation of fish and
wildlife practices will be provided by the SCS. An SCS project team
will consist of soil conservationists, an irrigation water management
specialist, engineers, a biologist, civil engineering technicians, and
soil conservation technicians. Additional technical assistance will be
provided by the CES.

Implementation of the Selected Plan will result in a reduction of an
estimated 52,900 tons of salt annually entering the Big Sandy River.
This will decrease salinity concentration in the Green River at the town
of Green River, Wyoming, by 27 milligrams per liter and decrease
salinity concentration by 5 milligrams per liter at Imperial Dam on the
lower Colorado River.

The Selected Plan will also increase hay production by an average yield
of more than 2 tons annually. Present average yields of hay vary from
1.6 tons/acre to 3.7 tons/acre. In addition to the increased yields,
irrigators will be able to maintain pure stands of alfalfa or higher-
value crops. These benefits will include: stands maturing earlier,
remaining productive longer, and may produce an additional cutting
yearly.

If 15,700 acres were converted to sprinkler irrigation, about 3,775 acres
of irrigation water induced and supplemented wetlands (USFWS Circ. 39,
Types 1, 2, 3, 4, 9, and 10) will be affected. See Glossary for
definition of wetland types. Typical wetlands in the project area are
shown in Figures 4-5 and 4-6 in Chapter 4. Reduced water supply will
occur on about 1,010 acres of wetlands, and 2,765 acres of wetlands
will be eliminated. The majority of the 3,775 acres of wetlands are
Types 1, 2, and 9. To replace wildlife habitat values foregone, the
habitat quality of about 860 acres of Types 3, 4, and 10 wetlands will
be voluntarily preserved and enhanced by pond lining, livestock
exclusion, seeding, and installation of nesting islands. Landowners,
the Irrigation and Drainage District, units of government, and private

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