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.., ) -- ~ '-:>- would not be significant. Results from Stage One would be evaluated before deciding to pro- ceed with construction of the rest of the unit. Stage One development would involve the concrete lining and rehabilitation of structures along a 6.S-mile section of the Government Highline Canal between Big Salt Wash and ~ack Wash in the western end of Grand Valley. Thirteen laterals that now serve the area under the canal section to be linea would be consolidated into 11 and placed in pipe sesctions. About 6.5 miles of interceptor ditch and four small detention ponds would be constructed above the canal section to prevent runoff from entering the canal. Some existing cross-drainage features would be enlarged. A field station would be constructed as part of the Stage One development for use as a construction headquarters and permanent operating facilities for the entire unit. To compensate for wildlife habitat losses, and area of suitable land would be acquired and initially developed, and a water- ing pond would be constructed above the Govern- ment Highline Canal. Data will continue to be gathered to determine the nature and extent of the salt loading to the Colorado River. Such data will include the following: (1) flow measurements and samples ........"'........ . "'--'-.J.O::)' UII.J.l October 9, 1979 Page 2 of 2 from all major "'ashes and drains j (2) samples and water levels from existing observation wells in the Reed Wash Study Area; (3) samples and water levels from an extensive network of wells valleywide; and (4) computation of water and salt budgets for the Grand Valley and for the Reed Wash Study Area. An extensive drtlling program has been com- pleted to obtain subsurface geologic data along all of the major canals in the valley. The core samples obtained will yield informa- tion on the pre8ence and extent of expansive clays, depths to water, and the type of sedi- mentary materials all of which will affect the engineering des::l.gn of the canals and laterals. LOCAL INTEREST Interest in the Grand Valley Systems Improve- ment Program by Federal, State, and local con- cerns is continually growing. In keeping with this interest, the Grand Valley Salinity Con- trol Coordinatir:g Committee meets regularly and is open to co.ll persons and agencies inter- ested in attending. The purpose of the com- mittee is to coe.rdinate all salinity studies and to dissemina.te information to the public. STATISTICS (TAKEN FROM DRAFT SPECIAL REPORT FOR STAGE ONE--STIlL UNDER REVIEW) EFFECTS ON THE COLORADO RIVER (average annual) Decrease in salt load (tons) . . . Reduction in depletion (acre-feet) Reduction in salt concentration at Imperial Dam from decrease in salt load (mg/L) , . , . . , , , 24,000 200 2,5 ESTIMATED COSTS PROJECT FEATURES Canal to be lined (miles). . . . Laterals to be improved (miles) Existing. . . . . . . After construction. . Detention ditch (miles). Detention ponds (number) 6.8 34.2 29.0 6.5 4 Oonstruction costs (January 1979 cos ts) Canal lining and improvement $8,325,000 Lateral improvement 8,455,000 Permanent operating facilities 420,000 Wildlife plan 750,000 Investigations prior to authorization 25,000 Irrigation Management Servicesll 25,000 Total. 18,000,000 Interest during construction (5 years at 5,625 percent) 700,000 Less costs of investigations prior to authorization -25,000 Total investment for economic analyses 18,675,000 .Annual equivalent costs (50 years at 5.625 percent) Construction costs 1,123,000 , Increased operation~ maintenance, and replacement costs 10,200 Total. 1,133,200 Cost per mg/L of salinity reduction at Imperial Dam 453,000 1/ Represents monies already expended, though the program will be discontinued after 1979.