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<br />:~ <br />"J~tt~~" <br /> <br />period to that for the 4":year period was derived from the feasibility <br />report studies of the Closed Basin Division. <br /> <br />Quality of Salvaged Water <br /> <br />During the investigations which preceded the issUance of. the <br />. U. S. Geological Survey Water Supply Paper 1379, "Ground water Resources <br />of the San Luis Valley, Colorado," samples of the shallow ground water were <br />obtained in and adjacent to the salvage area. Thirty-six of the samples, <br />obtained in the salvage area or Wi thin a mile of the boundary of the <br />salvage area and analyzed for both total dissolved solids and percent <br />sodium, show an average of 624 parts per million of total' dissolved <br />solids and an average. of 54 percent sodium. This percent sodium is <br />greater thanthelipiit{l.tion specified in'the Rio Grande COll\PB.ct that <br />Coloredoshall not be credited w,ith the amount of salvaged water <br />delivered to the Rio Grande from the Closed Basin unless the proportion <br />of sodium,ions is less than 45 percent of the total positive ions when <br />the total dissolved solids in the salvaged water exceeds 350 parts per <br />million. HoWever, when the water from the salvage area is comingled <br />with the 101,700 acre-feet of water salvaged from the Closed Basin <br />Division of' the San Luis Valley Project, which has a weighted quality <br />of' 162 parts per million of total dissolved solids and 28 percent <br />sodium, the total salvaged water from the Closed Basin would contain ' <br />an average of ab01,lt 239 parts per million of total dissolved solids <br />and about ~percent sodium. <br /> <br />;'1 <br />Plan of Development <br /> <br />Previous investigations of the ground water in the Closed Basin <br />have, shown that, although many variations eXi$t, the' first 'reasonablycon- <br />sistent clay layer, or aquiclude, is generally found at a depth of' some <br />70 to 80 feet. Above this depth lies a heterogeneous. mass df' material <br />containing discontinouB, lenticular clay layers. :Because of the discon- <br />tinuity of the clay layers in the first 70 to 80 feet of depth, water <br />from the deeper aquifers within this depth could move upward, as wel1. <br />as laterally, through the heterogeneous material and be consumed by non- <br />beneficial evapotranspiration. The plan of development for the Mosca- <br />Sargent area contemplates salvaging only that water above the aquiclude <br />that is now being consumed nonbeneficially. <br /> <br />Aquifer heterogeneity has been found to be so pronounced that '. <br />areas With specific aquifer characteristics cannot be delineated Without <br />drilling and testing almost' as ma.ny wells as would be required for a <br />proposed plan of development. In the more detailed studies made for the <br />Closed Basin DiviSion, using the results .from five test wells and all <br />other available ground water data, a tentative well field of 129 wells <br />was laid out over the 108,600-acre salvage area at spacings which varied <br />from one mile by one-half mile to one mile by two miles and averaged <br />about one well per 840 acres. For cost estimating purposes for the plan <br />of development of the Mosca-Sargent area, it was assumed that 36 wells <br /> <br />r...... ,. ," t <br />L ~ . ,,:.J:.t <br /> <br />,~ <br />