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<br />saturated soil samples taken from various depths do not indicate the presence <br />of undissolved salt. The vertical distribution of dissolved mineral <br />concentrations show the near-surface influence of Colorado River water and <br />deeper saline ground water. The incremental salt load appears to be resulting <br />primarily from the displacement of ancient saline ground water by the recent <br />application of fresh Colorado River irrigation water. <br /> <br />-6 Reclamation is currently examining drainage records to identify and <br />00 describe trends that would help predict a probable decline of the incremental <br />,__ salt load. These trends will help Reclamation, USDA, and PVID determine the <br />-J need for further studies. <br /> <br />17. Paradox Valley Unit (Reclamation) <br /> <br />Paradox Valley, a collapsed salt anticline, is a northwest-southeast <br />trending valley 3 to 5 miles wide in southwestern Colorado. Geologic <br />investigations in the Colorado Plateau have established the existence of a <br />series of five major northwest-southeast trending salt anticlines (elongated <br />swells), about 100 miles long. Paradox valley lies along the axis of one of <br />these salt anticlines and was formed from erosion of faulted and uplifted <br />sandstone and shale formations above a residual gypsum cap overlying about <br />14,000 feet of pure salt and salt-rich shale. The Dolores River remained in <br />its ancient streambed as the uplift and erosion of the valley developed. West <br />Paradox Creek heads in the La Sal Mountains and flows southeast through the <br />northwestern half of the Paradox Valley to the Dolores River. East Paradox <br />Creek, and intermittent stream, drains the southeastern half of Paradox valley <br />before flowing into the Dolores River. <br /> <br />Ground water comes into contact with the top of the salt formation <br />where it becomes nearly saturated with sodium chloride and surfaces in the <br />Dolores River channel in Paradox Valley. Studies conducted by the Bureau of <br />Reclamation have indicated that the river picks up over 205,000 tons of salt <br />annually as it passes through the valley. <br /> <br />In its definite plan report (September 1978), Reclamation <br />recommended that a series of wells be drilled on both sides of the river into <br />the brine zone to pump the saline ground water, lowering the interface between <br />the fresh ground water and the underlying brine. The brine would then be <br />stripped of hydrogen sulfide gas and pumped to a terminal evaporation pond in <br />Dry Creek Basin. <br /> <br />A draft environmental statement was prepared for this plan and made <br />public on May 11, 1978, with a final statement filed with the Environmental <br />Protection Agency (EPA) on March 20, 1979, and made public. Deep well <br />injection was one of the alternatives to pumping and evaporation of brine that <br />was discussed briefly in the statement. <br /> <br />Before installing permanent facilities, a verification pumping <br />program was initiated to determine, among other things, what pumping rate <br />would be required to redu3e the brine inflow. This program showed that by <br />pumping at a rate of 2 ft 1St apP3oxiroately 90 percent of the brine inflow can <br />be controlled. Initially, a 5-ft Is pumping rate was estimated to be <br />necessary to control brine inflow. <br /> <br />The projected lower pumping rate changed the criteria for evaluating <br />disposal methods. A private consulting firm completed a feasibility study of <br /> <br />VII-25 <br />