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