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<br />section on the cost of evaporation is inserted here. Througnout the Upper <br /> <br />....... . <br />m <br />w <br />~->. <br /> <br />Coloraca River Basin, evaporation is greater than precipitation. <br />net, evaporation rates are: <br /> <br />Some average, <br /> <br />Southern Utah <br /> <br />infyr <br />35 <br />40 <br />53 <br />60 <br /> <br />Colorado <br /> <br />Wyoming <br />New Mexico <br /> <br />There is a range o~ 35 to 60 in/yr. <br /> <br />needed to evaporate a few different <br /> <br />-5 2 <br />infyr (= 4.15 x 10 gals/(ft) (min) <br /> <br /> <br />acre-ft/(ft2) (yr) is: <br /> <br />For orientation, ~he approximate area <br /> <br />flow rates at a net evaporation rate of 35 <br />-2 2 -; <br />= 2.07 x 10 1:' sfft ) (hrJ = 6.68 x 10 <br /> <br />Flow Acoroximate Area to Evacorate <br /> . <br />Gal/Illin 103 lb/hr 106 ft2 A.cres <br />100 50 2.4 55 <br />200 100 7.2 111 <br />500 250 12.0 276 <br /> <br />Uncontrolled evaporation by spraying water with ash or for the purpose <br />of dust control has a modest cost, dependent on the distance over which the <br />water is pumped and the charge for using the land. Impoundment means an additional <br />cost because it requires dikes, scooping a pond and, most particularly, l~ning. <br />This is used extensively at coal fired power plants in the Western United <br />. 2 <br />States. Lined ponds cost about $l/ft (S43.000facreJ with the actual cost <br />being ve~p dependent on location and proximi~y ~o the source of clay :or <br />lining. ?olymer liners will be used where clay is too expensive. A financial <br />2 <br />charge of 8%/yr for 20 years gives an annual charge of about 10%/yr or $O.lO/(Et ) (yr). <br />Thus. evaporation pond charges are approximately $4.60/1000 gals evaporated (= <br />$0.55/1000 lb evaporated = $1500/acre-ftl. <br />If veri large ponds are required, they become distant from the plant and <br />the cost of pumping and of acquiring the land will go up. One alternative is <br />to first use forced evaporation to reduce ~~e quantity of wastewater treated <br />and then use a smaller evaporation pone for final disposal. In ~any modern <br />coal fired steam-electric power plants in the Western United States vapor <br /> <br />:5 <br />