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<br />. <br /> <br />. <br /> <br />. <br /> <br />Primary refinements and modifications of authorized Desalting Complex Unit <br />. -parameters presentedi n -this--StatusReport-, -compared-with .those presented <br />in the September 1973 Special Report, are: <br /> <br />1. The Desalting Complex Unit will be fully operational in 1981 instead <br />of 1978. <br /> <br />2. The annual Well ton-Mohawk Division irrigation drainage is estimated to <br />be 167,000 acre-feet with an average salinity of 3,200 parts per million <br />total dissolved solids (p/m TDS) in 1981 as compared with 175,000 acre- <br />feet at 3,100 plm in 1978. <br /> <br />3. The sal inity of water arriving at Imperial Dam in 1981 is estimated to <br />be 865 plm TDS, as compared with 910 plm in 1978. <br /> <br />4. Pretreatment for the desalting plant will require partial lime softening <br />and be more elaborate than originally conceived. <br /> <br />5. The membrane desalting plant will have the capacity to treat 144,700 <br />acre-feet of pretreated feed water at 2,904 p/m. The result will be <br />102,700 acre-feet of product at 386 plm and 42,000 acre-feet of reject <br />at 9,056 p/m. This compares with 144,000 acre-feet of feed water at <br />3,100 plm, 101,000 acre-feet of product at 240 plm, and 43,000 acre-feet <br />of brine at 9,600 p/m. <br /> <br />6. During normal operation the desalting plant is designed to recover 70.9 <br />percent of the feed water. The annual design plant product water volume <br />will be 61.5 percent of the Wellton-Mohawk Division drainage, while the <br />total combination of plant product and blend raw water returned to the <br />Colorado River will be 74.0 percent of the drainage. We believe that <br />from technical data provided to the Congress, the Special Report, and <br />from the legislative history, that this is consistent with the intent <br />of the Act (the second sentence of Section 101. (b) reads "The plant <br />shall effect recovery initially of not less than 70 percentum of the <br />. _ Q,=-aj!!_w~!~,=- ~~.Rroduct water. . . . ")-,--- __ ___ <br /> <br />7. The total desalting plant production capacity will be 108.5 million <br />gallons per day (Mgal/d), composed of 20.5 Mgal/d capacity spiral <br />wound reverse osmosis, 19.4 Mgal/d hollow fine fiber reverse osmosis, <br />22.9 Mgal/d electrodialysis, and 45.7 Mgal/d unspecified capacity seg- <br />ments. Including 90.7 percent plant factor, the plant will be capable <br />of treating about 138.7 Mgal/d feed water and producing 98.4 Mgal/d <br />product water, compared with 129 Mgal/d feed water and corresponding <br />90 Mgal/d product described in the Act. <br /> <br />8. The average annual plant product is prOjected to be 60,000 acre-feet <br />from 1982 through 1993. Corresponding average annual reject will be <br />26,000 acre-feet. After this initial critical period plant product is <br />projected to average 62,000 acre-feet annually, with 27,000 acre-feet of <br />reject. <br /> <br />2 <br />