There is hereby authorized to be appropriated the sum of $356,400,000 for the construction of the works and accomplishment of the purposes authorized in sections 1571, 1572, 1573, and 1579 of this title, of which $3,579,000 is authorized for mitigation of fish and wildlife losses associated with replacement of the Coachella Canal in California, and $6,960,000 is authorized for mitigation of fish and wildlife losses associated with the Desalting Complex Unit and the Protective and Regulatory Pumping Unit in Arizona, based on January 1979, prices plus or minus such amounts as may be justified by reason of ordinary fluctuation in construction costs involved therein, and such sums as may be required to operate and maintain such works and to provide for such modifications as may be made pursuant to section 1574 of this title. In order to provide for the utilization of significant improvements in desalinization technologies which may have been developed since the Bureau's evaluation, the Secretary is directed to evaluate such cost effective improvements and implement such improved designs into the plant operations when the evaluation indicates that cost savings will result: Provided, however, That no more than five percent of the amount authorized to be appropriated is used for these purposes. There is further authorized to be appropriated such sums as may be necessary to pay condemnation awards in excess of appraised values and to cover costs required in connection with the Uniform Relocation Assistance and Real Property Acquisition Policies Act of 1970 [42 U.S.C. 4601 et seq.].