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SUmARY SHEET f.r~'1..t~~L.~~~_~_~~;. Colorado River Uasin Salinity Control Projl'ct !larch 1980 Page 1 of 2 LOCATION . The Grand Valley Unit is located in west-central Colorado along the rC':lch of the Colorado River between the tmms of Palisade and Hack, arid includes Grand. Junction, the largest" city in western Colorado. PURPOSE The purpose of the Grand Valley Unit is to lower the salt loading to the Colorado River by concrete- lining canals and installing laterals in pipeline and installing "on-farm" improvements. The combi- nation of these programs would reduce the amount of ground water allowed to percolate into the under- lying highly saline soils and Bancos Shale For- mation. It is thought that the estimated 650,000 to 850,000 tons of salt added to the river annually. can be reduced as much as 60 percent by the imple- mentation of the above measures. STAWS The Grand Valley Unit is a component of the Colorado River Salinity Control Project and was authorized for construction by the Colorado River Basin Salinity Control Act of 1974 (Public Law 93-320). . A feasibility study in the Grand Valley was ini- tiated in FY72 to determine efficiencies of the conveyance systems to be gained by reducing the seepage losses. The various studies conducted include the follmdng: (1) determination of irrigated acreage; (2) canal and lateral sizing studies; (3) determination of the location, ca- pacitYt and condition of present canal and lateral structures; and (4) computations of quantities of construction materials. These data are being used to determine the feasibility level cost. estimate for the entire project. An ap- praisal level cost estimate has been made. Preliminary environmental studies have been con- ducted on the unit, and a Negative Determination of Environmental Impact was made by the Regiopal Director in June 1978 for an initial phase of the unit known as Stage One. The Commissioner concurred with the determination in July 1978. A Special Report for Stage One of the Grand Valley Systems Improvement Program has been completed. Stage One covers approximately 10 percent of the unit area and is designed to provide information to fully analyze the effectiveness of the proposed plan. The FY80 appropriations- include $4,127,000 for construction and monitoring of Stage One and continued planning of Stage Two. PLAN .' The preliminary plan for the overall Grand Valley Unit indicates that the salt loading of the Colo- rado River in the Grand Valley could be reduced by about 410,000 tons annually by decreasing the amount of irrigation return flows and conveyance system seepage moving through saline substrata and picking up sales. The reduction would re- sult in a decrease in the salinity of the river at Imperial Dam of approximately 43 mg/L and would be accomplished by a two-segment pro- gram conducted by the Water and Power Resources Service of the Department of the Interior and by the Soil Conservation Service of the Department of Agriculture. A Water Systems Improvement program would be conducted by the Water and Power Resources Servlee, in which canals aud laterals would be lined or placed in pipe to reduce seepage. Since only lined canals were included in the plan at authorization, the approval of Congress would be required to use pipe for those facilities. On-farm improvements, including upgrading irri- gation systems by cost assistance, improving irrigation management, improving grazing lands and grazing practices on private rangeland, and voluntary wildlife improvement measures, w.ould be conducted by the Soil Conservation Service to reduce deep percolation from farm operations. A wildlife area and watering ponds would be provided by the t~ater and Pmler Resources Service to compen- sate for wildlife habitat losses resulting from the Water Systems Improvement program. This wildlife measure was not included in the unit plan when it was authorized and would require the approval of Congress. STAGE ONE DEVELOP;ffiNT The unit would be developed in stages to allow the Water and Pm,'er Resources Service to begin con- struction in a portion of the valley ,.,here plans and designs are complete, 'vhere sufficient data are available to assess the impacts of the initial development while investigations and planning continue on the rest of the unit, and v7here environ- mental impacts would not be significant. Results " 10