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w rv CJ1 C0' Accomplishments in the Lower Colorado Reqion Point Source Division LaVerkin Springs Unit The LaVerkin Springs are located in a 1,800-foot-long reach of the Tempoweap Canyon of the Virgin River in southwestern Utah. The springs discharge about 8,300 acre-feet of water and 109,000 tons of salt each year. A feasibility study has been prepared that shows 103,000 tons of this salt could be removed annually which would eventually reduce total dissolved solids concentrations at Imperial Dam by 11 mg/l. A feasibility report on the LaVerkin Springs Unit is undergoing an in- house review at the present time. The plan of development calls for the construction of an upper diversion dam upstream from the springs to divert the normal river flows around the area. The lower control dam would be located just below the springs to form a pool from which the springs' flows would be pumped to the LaVerkin Desalting Plant. The average inflow to the reverse osmosis desalting plant would be 11.5 cfs through a 21-inch concrete pressure pipe. It will be necessary to pre- treat the incoming water in the form of calcium reduction. cooling, and filtration. The desalting unit would consist of three stages of vessels containing semipermeable membranes. Since the recovery of some water in each stage would increase the brine concentration passed to the succeeding stage, increasingly higher pressures would be required to effectively recover additional water. A product water of 8.3 cfs would be recovered at a salinity concentration of 500 mg/l. A brine discharge of 2.8 cfs is anticipated at a concentration of 33,000 mg/l. The product water would be returned to the Virgin River through a 1,600- foot-long pipeline. A l2-inch pipeline almost 19,000 feet long would be used to pump the brine to a 440-acre evaporation pond formed by diking a natural depression about 4 miles north of Hurricane, Utah. The dikes would be rolled earthfill embankments lined with 10-mil polyvinyl chloride. The entire pond would be lined with IO-mil PVC sheeting covered with 12 inches of earth. Littlefield Sprinqs Unit The Littlefield Springs discharge along the south side River about a mile upstream from Littlefield, Arizona. have a combined outflow of about 10 cfs and contribute of dissolved solids to the river system annually. of the Virgin These springs about 30,000 tons The disposal of these springs presents a special problem because the flow is presently diverted and used for irrigation in the Littlefield area. Feasibility investigations of this unit will start this year -B-