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DRAFT <br /> BRIEFING PAPER <br /> GRAND VALLEY UNIT, STAGE TWO, CRBSCP <br /> PRIVATE CANAL AND LATERAL SYSTEMS <br /> Purpose and Background <br /> The Grand Valley Unit was authorized for construction by the Colorado <br /> River Basin Salinity Control Act of 1974 (Public Law 93-320) as part of a <br /> basinwide effort to maintain water quality in the Colorado River for use in <br /> the United States and the Republic of Mexico. The Unit is located in west- <br /> central Colorado along the reach of the Colorado river between the towns of <br /> Palisade and Mack (see attached map) . The purpose of the unit is to reduce <br /> excessive salts entering the Colorado River caused by diversions and irri- <br /> gation of the Grand Valley lands. - <br /> Stage Development <br /> Stage One <br /> Stage One encompasses about 10 percent of the Grand Valley agricultural <br /> area and Stage Two the remaining 90 percent. Construction in the Stage One <br /> area was essentially complete by the start of the 1983 irrigation season. <br /> Construction included concrete lining 6.8 miles of the Government Highline <br /> Canal and installation of 12 pipe laterals. Also completed were canal cross <br /> drainage facilities, a moss and debris removed structure and the project field 0 <br /> station. Salinity and other environmental effects are being monitored to <br /> determine project construction impacts and to predict the future effectiveness <br /> of the program. <br /> Stage Two plan <br /> A course of action plan has been selected which provides for concrete <br /> lining of open laterals in all areas of Stage Two except the Redlands, and <br /> concrete lining the west end, middle, and`east end portions of the Government <br /> Highline Canal. Construction of the middle portion and east end of the <br /> Government Highline canal would be deferred until needed to meet the goals of <br /> the salinity control program. <br /> The construction cost of Stage Two is estimated to be $140,710,000 in <br /> January 1983 prices. About 40 miles of canal and 300 miles of laterals would <br /> be lined. The salt load to the Colorado River would be reduced by about <br /> 138,700 tons per year which would produce a reduction in salinity concen- <br /> tration at Imperial Dam of 14.1 mg/L. <br /> Wildlife measures consisting of watering ponds and acquisition of land to <br /> compensate for wildlife habitat losses are under consideration by Congress. <br /> 1 <br />