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" o P\) OJ \1) exploring foundations. locating .construction materials, and determining cross drainage requirements. Data collected will be used to complete the fi~al design and to prepare specifications for construction. Construction on these features is expected to begin in 1986. 12 pipe laterals. Also completed were QrOS8 drainage facilities, a moss and debris re~oval structure snd the Grand Valley f{eld stat~on. To assess the effects of Stage One improve- ments on ground-water flows and' water quality, a hydrologically isolated basin--the Reed ~ash study area--has been equipped to mon~tor surface snd ground-water inflows snd outflpws. . The amouut of salt picked up wichin this basin after the canal snd lateral improvements is compared to the amount picked up prior to>the improvements, the,differ~nce constit.uting ,the r~duction of salt loading due to Stage One . '~~'deve lopment. <,wild 1 ire 'resources are also being; monitored in the S-tage One area' to determine the effects of Stage One improve- .>Ql.erits 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 Uni~ed States and the Republic of Mexico. The p-urpose 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 Serv~ce. The water systems improvement segment is being directed by Reclamation while the on-farm improvement portion, consisting of upgrading irrigation systems and improving irr igat ion management, is being conducted by ses. Stage Two investigations began in Nove~ber 1981 and have included various hydrologic) engineering, and environ~ental studies as well as formulation and evaluation of alternac-ive plans. A wide range of general salin;ity control measures were considered inclu4ing concrete lining or placing laterals in p(pe, concrete and/or ,membrane lining canals, installing barrier c,~toff 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) ",here monitoring could be conducted to assess the effects of initial development, a~d where environmental impacts would be minimal. Planning on the remainder of the Grand Valley Unit could then continue concurrently. REPORTS The definite plan rep9rt for the Stage One water systems improvement program was prepared in March 1980. Preliminary .environment.al studies led to a negative determination .of environm~ntal impa~t for Staee On.e 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 repor.t 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 Octob,er 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 c, i .1 i , i , " 1-' "'~ ';' , @ t , " ;0. ~ h . , '~ I