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introduction...THE PROBLEM , . .". ~.. -.-'" . ~" .' '"" "... ,"t' ~. . Paradox Valley is located on one of five major salt anticlines located throughout southwestern Colorado and southeastern Utah. These salt anticlines are geologic formations that are the remnants of ancient salt lakes. similar to the Great Sal t Lake in Utah. The lakes evaporated away approximately 300 million years ago. leaving thick salt formations behind. Beneath Paradox Valley, the nearly pure salt and salt-rich shale formation is 14.000 feet thick. The formation is overlain by about 100 feet of gravel stream deposits that form the valley floor. Ground water flowing toward the Dolor- es River comes into contact with the salt formation and surfaces as salt brine in the river channel near the middle of the valley. The concentration of the brine is approximately 7 1/2 times that of the ocean (ocean water contains 35,000 milligrams/liter of total dissolved solids). Over 200,000 tons of salt enter the river throughout the valley annually. 1 Location Mop-I hi story". THE PLAN purpose."SALINITY CO~TROL In 1979, a Definite Plan Report and Environmental Statement were completed and approved. The plan called for pumping brine from wells paralleling the Dolores River and adjacent to brine inflow areas and disposing of it in a large evaporation pond in Dry Creek Basin. Approximately 180,000 tons of salt per year, an amount achieving a favorable benefit-cost ratio for the project, would be removed from the Colorado River. Before installing permanent facilities to accomplish this. however, a pumping program was initiated to determine. among other things, what pumping rate would be required to reduce the brine inflow. These tests have indicated that a disposal al- ternative other than the original plan might work better. The Paradox Valley Unit of the Salinity Control Program is designed to reduce the valley's contribution to high salinity levels in the Colorado River. Salt concen- trations in the Colorado River have been increasing. particularly in the lower reaches, as a result of man1s use and reuse of the river. The river carries about 10 million tons of salt each year, causing problems for water users because of lower crop yields and increased treat- ment costs. 00 277