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CRBSCP, Protective and Regukllory' Pumping Unit t;.> <;:) '"'-1 0',) and its design capacity increases 8S it passes each well. The concrete-lined open channel has a lining thickness of 2.5 inches and a bottom width that ranges from 4 to 6 feel. Water depths Tange from 2.8 to 5.8 feet with water velocities from 3.6 to 4.8 feet per second. Two settling basins have been constructed within the open channel portion of the lateral to provide storage capacity for the accumulation of 6ediment, mostly windblown sand. A .stand box, 8 vertical open structure which serves as a re- lief vent, is located at each well site along the pipeline to eliminate water hammer. The end of the 242 con- veyance channel, the terminal discharge pipeline, is a 72-inch reinforced concrete pipe designed to carry 220 cubic feet per second of pumped water. Attendant Facilities A 12-mile-long access road was constructed along side the 242 Lateral and the well sites. This road serves the construction, operation, and maintenance of the unit facilities. The Department of Energy's Western Area Power Administration (W APA) has constructed a 69-kilovolt transmission line east of Yuma to WAPA's Sonora Substation, located about 18 miles south and slightly west of Gila Substation. The Sonora Substation is also located about 2.5 miles north of well 242-22, the eastern end of the well field. To distribute power to the existing well pumps.. a 34.5-kilovolt transmission line connects Sonora Substation with the 34.5-kilovolt transmission line constructed next to the access road and conveyance system. The 34.5-kilovolt electrical distribution system also connects to the Yuma County Water Users' Associa- tion's system at the western end of the well field. The W APA facilities were completed in 1983. ~rater deliveries to Mexico at the Southerly Interna- tional Boundary will be coordinated with deliveries to the Northerly International Boundary located between California and Mexico. This will minimize overdeli,'eries to Mexico. Fish and Wildlife The development of the Protective and Regulatory Pumping Unit (and also the Desalting Complex Unit) will result in the loss of fish and wildlife habitat. Mitigation measures will replace about 65 percent of these losses. The mitigation measures were not originally authorized under Title I of the Colorado River Basin Salinity Con. trol Act, but are included in amendatory legisJation ' _ Public Law 96-336, dated September 1978, DEVELOPMENT Hiatory During the negotiations between the United States and Mexico that were to resolve the salinity problems of the Colorado River water delivered to Mexico (Minute No. 242), the United Slates Government brought to the aUention of the Mexican Government that the ground water underlying the United States was being withdrawn by Mexican pumping. This was due to operation of a I well field that Mexico had installed immediately south of the Southerly International Boundary. It was recognized by the United States that this withdrawal of ground water would significantly affect the United States in several areas, particularly since Mexico expressed the intention to continue pumping from the well field to supply irrigation water to Mexican agricultural lands. Among other things.. Minute No. 242 stipulates that the United States and Mexico will limit ground-water pumping within each country to 160,000 acre-feet an- nually within 5 miles of the Arizona/Sonora border. By pumping these waters, Mexico withdraws ground water from the United States without credit for delivery of water from the United States to Mexico in accordance with treaty obligations. Yuma Valley agricultural drainage and rrngation waste are delhrered to the Mexjcan canal system and are credited toward the 1.5 million acre-feet-per-year delivery I requirement of Colorado River water to Mexico. Histori. call}', these annual fJows have been about 125,000 acre-feet of drainage returns and 15,000 acre.feet of regulatory waste (unused irrigation water) from the Y urns CanaJ system. Pumping by Mexico and the United States has lowered the ground.water elevations and is I reducing the amount of drainage underflows from Yuma Valley. The annual combined flow of about 140,000 acre-feet per year at the Southerly International Boun- dary will gradually decline to only 15,000 acre-feet per year. The Protecth'e and Regularory Pumping Unit is intended to maintain deliveries near the 140,000 acre-foot level. To maintain the treaty flow to Mexico, any reduction in deliveries at the Southerly International Boundary would have to be made up at the Northerly Interna- tional Boundary by increased deliveries of water from I other sources. Under present conditions, this can be done only by releasing additional stored river water not now committed to Mexico. In compliance with Minute No, 242 and Section 103 (a) of the Colarado River Basin Salinity Control Act of 1974, a memorandum report was prepared on protective and