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The mining of uranium is carried out in widely separated parts of the world, including, surprisingly, the Gulf coastal plains of Texas. The mining method used to actually recover uranium varies depending on ore type, the geology of the area and other local factors. Open pit mining is preferred when the uranium exists in abundant amounts close to the surface. When the uranium occurs in veins deep under ground, box cut or underground tunnel mining is preferred. The most common method employed along the Texas Gulf Coast is called in-situ leaching (ISL). This method leaves the main body of the ore in place and removes the uranium by dissolving it in an appropriate solvent and then pumping it out of the ground. The solvent most commonly used is oxygen-saturated water containing an acid such as sulfuric acid or a base such as sodium bicarbonate. This method obviously requires that the ore body is located in a matrix that is permeable to the solvent. This type of matrix generally has associated groundwater. ISL methods are attractive when the ore is of low grade and other methods are too expensive to be profitable. The downside is that the associated groundwater away from the ore body could be contaminated. Although in-situ leaching is highly regulated both by the state and by the federal government, the regulations that have been followed for more than 30 years appear to be faulty and do not adequately protect the local groundwater from excessive contamination by uranium and radium. Showing that to be true is the main focus of this paper.
Most current U.S. ISL uranium production is from mines in Wyoming and Texas. According to the Nuclear Energy Agency (2008), 38 percent of U.S. uranium reserves are classified as ISL amenable. Thus, the safe and effective use of ISL technology in mining uranium deposits is a potentially critical element in the movement towards energy independence in the United States.
My interest in ISL mining and its problems was originally generated in response to a legal question concerning the validity of reported baseline values of certain chemical constituents, primarily uranium and radium, in the groundwater within a proposed mining permit boundary. These concentrations were submitted by the Uranium Energy Corporation (UEC) as required information in an application to the Texas Commission of Environmental Quality (TCEQ) for a permit to conduct in-situ mining of uranium in Goliad County, Texas. Although the discoveries I have made were obtained from data specific to this mine in Texas, I believe that the results are generally valid for all such mining operations regardless of location.
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