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. . . During .the planning phases of the Uintah Basin Salinity Control project in the late 1970's, USDA-SCS addressed the salt load contribution to the Colorado River resulting from on-farm irrigation. The Bureau of Reclamation was charged with the evaluation of canals and laterals which deliver irrigation water from the source to the farm. However, there was an interagency agreement which allowed SCS to treat part of the laterals with pipelines to the extent necessary to provide needed gravity pressure to operate the on-farm surface and sprinkler irrigation system's to be installed under the USDA plan. The USDA Uintah Basin Salinity Plan addressed specifically the on-farm salt contribution to the Colorado River. The plan identified salt reduction benefits at Imperial Dam as the sum of actual salt load reduction leaving the project and the dilution effect of undiverted water leaving the project. The total downstream benefit at Imperial Dam resulting from USDA on-farm projects was calculated to be 10.3 mg/l. 76,000 tons on-farm salt load reduction 20,200 ac. ft. undiverted water (dilution) Total = 7.95 mg/l = 2.35 mg/l 10.3 mg/l It was determined after the plan was published and authorized that downstream salt concentration reduction benefits resulting from the dilution effect of undiverted project water was not valid. However, there has been no official attempt to modify the 10.3 mg/l impact at Imperial Dam. Also, after the USDA-SCS plan was published, authorized, and implementation had started, SCS & BR reached new agreements over the division of responsibility for evaluation and treatment of canals and laterals. SCS was given additional responsibility to evaluate and propose treatment of specific reaches of laterals and canals. SCS entered into a lateral study activity which was ultimately intended to develop a supplement to the USDA Uintah Basin Salinity Plan. As the planning activities progressed, it became evident that most of the lateral treatment which SCS considered cost effective was already being treated under the authorized plan and the cost for treating those laterals were included in the original plan. Under the original plan, in excess of 300 miles of irrigation laterals were being lined with pipelines in order to provide the needed gravity head pressures to operate the on-farm irrigation systems and the cost of installing these supportive pipelines was included in the original plan. However, there had been no attempt in the original USDA plan to claim any salt load reduction benefits resulting from reduced seepage loss of the 300 miles of improved laterals. -2- 00[635