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-. i-" ,-, r', - ~U~V MEMORANDUM To: riles Subject: Response to the July 8, 1974, Environmental Protection Agency (Region VIII) Letter of Comment on the Fryingpan-Arkansas Project, Colorado, Draft Environmental Statement A major effect on implementation and operation of the Fryingpan-Arkansas Project (FAP) is the impact upon salinity of the waters in the Colorado River Basin. EPA offers the following comments regarding the salinity increases as they affect economic and environmental factors due to the diversion of 70,000 acre-feet annually: 1. Comment - The consumptive use of this amount of high quality water (50 mg/l dissolved solids) will result in a Bureau of Reclamation estimated increase of 4 mg/l of total dissolved solids, at Hoover Dam, Arizona. Data and calculations made to arrive at this estimate should be included, at least in the appendix of the final report. . Response: Data and calculations are included in revised Chapter IV. Data and calculations are presented for Cameo, Colorado, Lees Ferry, Utah;and Imperial Dam, Arizona. 2. Comment - Recommendations of the 1972 Colorado River Enforcement Conference and the proposed Colorado River System Control Policy and Standards Procedures published in the Federal Register June 13, 1974, both call for the establishment of a policy to~maintain salinity at or below 1972 levels in the lower main stem of the Colorado River. Because this project will result in an increase in salinity, potential measures to offset these increases should be discussed in the final statement. Response: Public Law 93-320 has authorized four salinity control units with an estimated combined impact of 48 mg/l reduction in salinity at Imperial Dam. Two of these projects, Grand Valley Unit and Paradox Valley Unit, are located in Colorado and would result in a projected 35 mg/l improvement in concentration at Imperial Dam. A discussion of these units, background material for which may be found in "Colorado River Water Quality Improvement Program Status Report, January 1974," follows: . Paradox Valley Unit, Colorado - Paradox Valley contributes about 200,000 tons of salt per year to the Dolores River in southwestern Colorado. A control project would reduce this contribution about 180,000 tons per year resulting in a reduction of the salinity concentration at Imperial Dam of about 16 mg/l. Investigations were started in fiscal year 1972 and a feasibility report is scheduled for completion in fiscal year 1975. XI-279