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<br />N <br />Ut <br />en <br />0,') <br /> <br /> <br />Energy Exploration and Development <br /> <br />Many of the geologic formations of the Colorado River Basin were deposited in marine <br />(salt water) or brackish water environments. Sulfates and sodium chloride are <br />prevalent salts in most of these formations, Many of the formations were deposited in <br />drier periods and are capable of transmitting water, but these aquifers are frequently <br />sandwiched between hundreds or even thousands of feet of impermeable shales <br />(aquicludes). These aquifers are, therefore, static and often saline. Many static and <br />saline aquifers are present in the Colorado River Basin. When a path of flow is <br />provided by drilling or mining, these aquifers are mobilized, and brackish or saline <br />waters flow back to the surface. <br /> <br />The development of energy resources, specifically coal, oil and gas, and oil shale, in the <br />Colorado River Basin may contribute significant quantities of salt to the Colorado <br />River. Salinity of surface waters can be increased either by mineral dissolution and <br />uptake in surface runoff, mobilization of brackish ground water, or by consumption of <br />good quality water. The location of fossil fuels is associated with marine-derived <br />formations. Any disturbance of these saline materials will increase the contact <br />surfaces allowing for the dissolutions of previously unavailable soluble minerals. <br /> <br />Salinity increases associated with the mining of coal can be attributed to leaching of <br />coal spoil materials, discharge of saline ground waters, and increased erosion resulting <br />from surface disturbing activities. Spoil materials have a greater permeability than <br />undisturbed overburden, allowing most of the rain falling on the spoils to infiltrate <br />instead of running off. The water percolates through the spoils, dissolving soluble <br />minerals. <br /> <br />Studies[5-7] conducted on mining spoils in northwestern Colorado indicate that the <br />resulting salinity of spoil-derived waters ranges from approximately 3,000 mg/L to <br />3,900 mgIL. The variability in concentration depends on water residence time and the <br />chemical and physical properties of the spoil. <br /> <br />Saline water is also a byproduct of oil and gas production in the Basin. It is not <br />uncommon to produce several times the amount of saline waters as oil. Oil and gas <br />operators in Colorado produced approximately 25,000,000 barrels of saline water <br />during December 1985. The salinity of production waters varies greatly from location <br />to location and is dependent upon the producing formation. Common disposal <br />techniques include evaporation, injection, and discharge to local drainages. <br /> <br />The future development of the oil shale resources in Colorado, Utah, and Wyoming has <br />the potential to increase salt loading to the Colorado River. Salt increases can be <br />attributed to the consumptive use of good quality water, mine dewatering, and, if <br />surface retorting is used, the leaching of spoil materials similar to that of surface coal <br />mining. <br /> <br />Reclamation and others are attempting to identifY abandoned exploration wells that <br />are leaking and develop plans to control the leaks. The Meeker Dome Salinity Control <br />Unit identified and plugged several abandoned wells along the White River to prevent <br />a salt dome (a geologic formation) from discharging saline water into the river. <br /> <br />12 <br />