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, ,.... ,-. '7 li..J. , One alternative plan for reducing the contribution of salinity of Las Vegas Wash Groundwater consists of groundwater interception facility, delivery pipeline, pumping plant, evaporation pond, and surface flow bypass system. 'I'his solar evaporation plan is estimated to reduce the salt contribution of the wash by 1)1,000 tons annually. The groundwater flow, which surfaces at a narrow point in the wash, would be collected in a series of subsurface drains and pumped 4 miles to evaporation ponds, comprising some 2,)00 acres in the vicinity of Henderson. I~aximum annual evaporation, which is expected to be reached in the year 2000, will be about 15,000 af/yr. The treated effluent from the municipal treatment facilities, which has a much lower salinity than the groundwater, would be collected, bypassed around the area of rising groundwater, and allowed to discharge into Lake Mead. Implementation of the project will reduce salinity of the water to downstream users. The ~rash is highly valued as a recreational and wildlife habitat area. Continued return of treated effluents will maintain year-round flow of the wash below the area of rising ground water. The estimated cost of the proposed salinity reduction program is $49.1: million vlith an annual operation, maintenance and replace- ment cost of $200,000. Total capital costs, including interest during construction, ~lOuld be $5L,., 700, 000, and the annual costs, based on amortizing the capital costs at 6 7/8 percent interest over 100 years, \vould be $l" 000, 000. The removal of 1)1,000 tons a year of salt from the river would reduce the river's salinity at Imperial Dam by I) ppm. In another alternative, the collected groundwater flows would be directed by the drains to a main sump where they would be pumped to a reverse osmosis desalting' plant. The -product stream of vlater ~ith a salinity of 500 mg/l would be returned to the Vash, and the brine stream would be delivered to a disposal pond for evaporation. \nth a brine dischare;e of about 1,900 af/yr, about 28) acres of ponds w)uld be required to evaporate the brine waters. This alternative WGuld remove about 1)8,000 tons of salt per year from the salt load discharged by the Hash to Lake Mead. A third alternative calls for disposal of the collected ~round- 'vater flows in Dry Lake, a playa, northeast of Las Vegas. Joint use of the proposed pipeline to convey effluent from the waste treatment plant near Las Vegas to the Allen Power Project for power plant cooling is proposed. Colorado River Water Quality Standards Lynn M. Thatcher, Chairman of the Colorado River Basin Salinity Control Forum, sent a letter dated November 26, 197), to ~~. Paul - 19 -