WSP05094

• File Number: 8277.600.10
• Description: Big Sandy River Unit - Colorado River Salinity Control Program
• State: WY
• Basin: Colorado Mainstem
• Date: 2/1/1988
• Title: U.S.D.A. Selected Plan - Big Sandy River Unit
• Water Supply Pro - Doc Type: Definite Plan Report

Installation of planned measures reduces average annual salinity damage
to the Lower Colorado River Basin by $2,834,100 and to the Green River
in Wyoming by $489,000. The benefits for the Lower Colorado River Basin
were based on the 1986 value of $566,820 per year per mglL of salinity
reduction at Imperial Dam, California. The $566,820 per mglL was
derived from damage esti.mates and control program impacts prepared by a
consortium of Water Resources Centers in Arizona, California, Colorado,
and Utah. The benefits on the Green River were based on interview data
with the Jim Bridger Power Plant, Trona Plants near Green River, and the
towns of Green River and Rock Springs. Reduced water treatment costs to
these industries and towns is estimated to be $18,335 (1986 value) per
mg/L.

Average Annual project costs are estimated to be $2,170,600 (50 years
at 8 5/8 percent interest). The net beneficial effect of the project
is $2,471,300 annually. See Tables 4-5 and 4-6 for a more complete
reference of costs and benefits of the Selected Plan.

Installation Schedule and Other Project Activities

The project will be installed over a 9-year period. SCS technical
assistance will begin 1 year prior to installation of salinity control
practices and continue for 2 years after the practices have been installed.
The installation schedule for the Selected Plan is shown in Table 4-7.
The SCS will assist program participants with the development of individual
or group salinity control plans (SCP). These plans will identify the
type and extent of practices needed for salinity control and those for
the voluntary replacement of fish and wildlife values. Planned practices
that are applicable to each farm or operating unit will be included in a
long-term salinity control contract based on the SCp's between the USDA
and the landowner.

The installation of the proposed canal and lateral wasteway and regulating
reservoir systems will be an off-farm installation. They will be installed
in stages as onfarm project participation develops in specifi.c areas. Upon
completion of onfarm sali.nity control measures, it is estimated that four
to six wasteways and four to seven regulating reservoirs will have been
installed to provide Eden Valley Irrigation and Drainage District with the
ability to efficiently manage their irrigation system. The wasteways will
control the 400 cfs flow in the canals and laterals by dumping water into
15 to 20 miles of intermittent flowing natural drainages if the area
suffers extensive power outages. The regulating reservoirs will regulate
canal flows and will be lined. They will have a water surface area of 150
to 300 acres and regulation storage capacity of 200 to 300 acre feet. The
wasteways and regulating reservoirs will be located throughout the project
area.

The SCS will provide technical assistance for designing, constructing, and
certifying completion of practices identified in the long-term contracts.
The Ases will administer the cost-share provisions of the long-term contracts.

Conflicts between improved irrigation and loss of wetlands will be
identified as part of the case-by-case envi.ronmental evaluation which SCS

4-8

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