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<br />Phases 1 and 2 when combined (without increased cotton acreage) <br /> <br />would reduce the :peak salt concentrations in the water delivered to <br /> <br />Mexico to about 1,800 ppm, while still maintaining satisfactory <br /> <br />ground-water conditions within the District. Reduced drainage <br /> <br />pumping associated with increased cotton acreage, if combined with <br />Phases 1 and 2, would :t'urther reduce the peak salinity. The esti- <br />mated cost of Phase 2 construction is $30,000,000. Of this amount <br /> <br />it is estimated that $21,000,000 is for the flood-control channel <br /> <br />and dikes. <br /> <br />Phase 3 involves totaJ. overalJ. river regulation on the Lower <br /> <br />. <br /> <br />Colorado River and would consist of integrating ground-water pumping <br /> <br />" <br /> <br />with the river regulation that will be provided by Senator Wash <br /> <br />Regulatory Reservoir now under construction. <br /> <br />The studies on which the above recOllllllendations are made included: <br /> <br />(1) periodic water sampling and analyses from selected locations on <br /> <br />the Colorado River and on drains providing return flow to the river <br /> <br />below Hoover DllII1j (2) f'orty-nine 12-inch test wells drilled to an <br /> <br />average depth of 130 feet trom which both water and soil samples <br /> <br />were collected at varying depths to evaJ.uate in detail. the quantity, <br /> <br />quality, and locfd;ion of ground water underJ.ying the Wellton-Mohawk <br /> <br /> <br />ValJ.eyj (3) numerous shalJ.ow test borings in both the irrigated and <br /> <br />. <br /> <br />nonirrigated areas of the Wellton-Mohawk District from which soil <br /> <br />., <br />'t, <br /> <br />and water samples were taken to evaluate the degree of land recla- <br />mation accomplished and rPmAining to be accomplishedj (4), a field <br /> <br />study of soils in the Mexicali ValJ.ey, which was limited by Mexico <br /> <br />to one week, during which samples were collected from 20 type <br /> <br />locations and subjected to detailed laboratory anal.yses j <br /> <br />iv <br />