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<br />Uur drilling program <br /> <br />near <br /> <br />the ~iver has produced information <br /> <br />indicating a general rise or subsurface ridge of the Paradox Member <br /> <br />extending parallel along the middle of the valley and perpendicular to the <br /> <br />river. Going both upstream and downstream from the ridge the alluvium <br /> <br />tnickens. This ridge coincides very closely with the downstream side of <br /> <br />an upper concentrated brine inflow area. Also, near the downstream end of <br /> <br />tile valley, the alluvial material thins and the Paradox Member rises <br /> <br />almost to the surface. This area coincides witn the downstream side of a <br /> <br />lo~er concentrated brine inflow area. <br /> <br />Samples and studies show that in east Paradox Valley little, if any, <br /> <br />fresh water overlies the brine. However, in West Paradox Valley there is <br /> <br />a significant fresh water lens overlying the brine. At the inflow areas, <br /> <br />the brine-fresh water interface intersects the river near its bottom. <br /> <br />Going West away from ttle river the fresh water lens thickens and i~ <br /> <br />approximately 100 feet thick 1 mile west of the river. <br /> <br />A conceptual model of the ground water and salt transport can be <br /> <br />illustrated with a cross-sectional flow net. Water level and piezometric <br /> <br />head contour maps of the water table and ground water system indicate that <br /> <br />water, both fresh and brine, is flowing toward the river from both East <br /> <br />and West Paradox Valley (refer to Figure 2). Note that in West Paradox <br /> <br />VaLley, the interface between the brine and the fresh water does not <br /> <br />coincide with a flow line. <br /> <br />This reflects our belief that the dissolution <br /> <br />of salt and the formation of the sodium chloride brine primarily Occurs <br /> <br />near the contact between the residual cap (gypsum breccia) and the <br /> <br />underlying halite beds. The flow net also indicates that the recharge in <br /> <br />areas farthest from the Dolores River tends to follow flow lines to the <br /> <br />deepest part of the aquifer, and it is this recharge that needs to be <br /> <br />controlled to reduce brine inflow. Depending on location of the recharge <br /> <br />source, travel time could vary from months to even hundreds of years. <br /> <br />00(561) <br /> <br />4 <br />