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<br />, <br />~ <br />'"', <br />~ . <br />C": <br /> <br />"- <br /> <br />c <br />c <br /> <br />Option IA, the least cost alternative, is that selected by the <br />report as its recommended plan. It results in the return to the <br />lake of up to 29,000 to 34,000 tons of salt per year in a manner so <br />that maximum salt dispersal is achieved into Lake Powell. The next <br /> <br />least cost alternative, Option 2A, would first increase the concen- <br />tration of the blowdown water and then provide for its evaporation <br />in impervious ponds. The present worth of its cost would be $5.55 <br />million more and annual costs would be about $400,000 per year more <br />than the least cost alternative. The unit cost of salt removal would <br /> <br />be sliehtly more than $13 per ton per year. <br />Alternative 30. which incorporates an electrodialysis treatment <br />plant that salvages 75 to 80 percent of the 3650 acre-feet per. year <br />of blowdown water, is only slightly more expensive than Alternative <br />2A, Its present worth of all costs is $5,66 million more than the <br />least cost alternative, and represents a unit cost of salt removal <br />of about $13.50 per ton per year. <br /> <br />The next most expensive alternative, Option 4C, incorporates a <br />flash evaporator for treatment of the blowdown water so that only a <br />minimal quantity of blowdown water would be lost for reuse. This <br />option costs about $6.08 million, present worth, more than the least <br /> <br />cost alternative, and represents a unit cost for salt removal of <br /> <br />about $14.50 per ton per year. <br />Analysis of these four options shows that the bulk of additional <br /> <br />cost over the least cost alternative is involved in moving to the <br />next least cost alternative of evaporation ponds with pretreatment. <br />Thereafter, the increase in cost for the next two options is small. <br /> <br />-5- <br />