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o O;J go N '- c:- exploring foundations, locating construction materials, and determining cross drainage requirements. Data collected will he used to complete the final des ign and to prepare specifications for construction. Construction on these features is expected to begin in 1986. 12 pipe laterals. Also completed were cross drainage facilities, a moss and debris removal structure and the Grand Valley field station. To assess the effects of Stage One improve- ments on ground-water flows and water quality, s hydrologically isolated basin--the Reed Wash study area--has been equipped to monitor surface and ground-water infloW's and outfloW's. The amount of salt picked up within this basin after the canal and lateral improvements is compared to the amount picked up prior to the improvements, the difference constituting the reduction of salt loading due to Stage One development. Wildlife resources are also being monitored in the Stage One area to determine the effects of Stage One improve- ments on vegetation and wildlife. THE GRAND VALLEY UNIT BACKGROUND The Grand Valley Unit was authorized for con- struction by the Colorado River Basin Salinity Control Act of 1974 (Public Law 93-320) as part of a basinwide program aimed at enhancing and protecting the quality of water available for use in the United States and the Republic of Mexico. The purpose of the unit is to reduce salt loading to the Colorado River from the Grand Valley Unit area. To accomplish this salt reduction. a two-segment program is being conducted by the Bureau of Reclamation and the Soil Conservation Service. The water systems improvement segment is being directed by Reclamation while the on-farm improvement portion. consisting of upgrading irrigation systems and improving irrigation management, is being conducted by SCS. Stage Two investigations began in November 1981 and have included various hydrologic, engineering, and environmental studies as well as formulation and evaluation of alternative plans. A wide range of general salinity control measures were considered including concrete lining or placing laterals in pipe, concrete and/or membrane lining canals. installing barrier cutoff walls and combining irrigation systems. Development of the water systems improvement measures was planned in stages so that con- struction could begin in a portion of the valley where plans and designs were complete, where monitoring could be conducted to assess the effects of initial development. and where environmental impacts would be minimal. Planning on the remainder of the Grand Valley Unit could then continue concurrently. REPORTS The definite plan report for the Stage One water systems improvement program was prepared in March 1980. Preliminary environmental studies led to a negative determination of environmental impact for Stage One which was rendered by the Regional Director in June 1978; the Commissioner concurred with the determination in July 1978. In June 1983, a supplement to the March 1980 definite plan report was prepared. A final environmental statement on the entire unit will be filed in January 1986. Stage One construction, which involved about 10 percent of the unit area. began in October 1980 and was essentially complete in April 1983. Development included concrete lining of 6.8 miles of the Government Highline Canal and consolidation of 13 open channel laterals into