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

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experiment in desalting by natural freezing was conducted. In 1974, the
atmospheric freezing experiment attempted to separate fresh water and
brine. The experiment encountered problems with maintaining equipment
operating under freezing conditions, separating the brine flow,
evaporation of brine, and most importantly, pointed out the need for
lined collection ponds.

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The USBR drilled a total of 100 test wells between 1975 and 1978 to
locate and characterize the various saline aquifers. These holes range
in depth from 30 to 300 feet and cover an area that extends from the
Big Sandy Reservoir to the Gasson Bridge on the Big Sandy River, which
is a distance of about 2S miles. The wells have been monitored for
water level and quality. All the test wells have been pump tested to
determine the extent and transmissibility of the aquifer. The ground
water levels in the project area respond quickly to irrigation. The
water table rises when water is turned into the Eden Valley irrigation
project in the spring and recedes in the fall. The magnitude of rise
and fall depends on climatic conditions and water supply delivered to
irrigation project in any given year.

Eighteen of the test wells were drilled near the Big Sandy Reservoir.
It appears that the reservoir does not contribute significantly to the
salinity problem. Pump testing of wells above the Eden Project indicate
only minor contributions from that area.

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The bulk of the aquifer discharge occurs along a lS-mile reach of the
Big Sandy River in the form of seeps, springs, and flowing wells.
Investigations indicate that approximately 27 cfs surfaces and flows
back into the river along this reach. The USBR has drilled three
lS-inch-diameter wells near the larger seeps in the "Big Bend" area
between Simpson Gulch and Gasson Bridge. These wells were tested with
S-day pump tests at rates from 825 to 2,700 gallons per minute. The
total dissolved solids concentration varied from 4,000 mg/L to 5,SOO mg/L.
The flow in the seep area was dramatically reduced during the pump tests.
However, disposal of the saline water remains a major hurdle to a satis-
factory salinity control for this type of project. In 1982, the USBR
evaluated the delivery of saline underground water from the Big Sandy
area to Chevron Chemical Company and Texasgulf Chemicals, Inc., near the
towns of Rock Springs and Green River. However, both of these companies'
plans indicated that the use of Big Sandy water was not needed. During
1984 and 1985, the USBR investigated the use of saline Big Sandy water
for the Jim Bridger Power Plant. This alternative was found to be
economically unattractive because of the long and expensive delivery
system required to transport the water to the Jim Bridger Power Plant.

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The USBR has concluded its studies and, at the present time, does not
anticipate recommending construction of off-farm salinity control
features. If the need for additional salinity control develops in the
future, installation of off-farm features in the Big Sandy Unit may be
considered further if the more cost-effective units in the Colorado
River Basin have already been developed.

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