INVESTIGATION OF URANIUM OCCURRENCE IN SURFACE WATER AND GROUNDWATER IN SOUTH TEXAS

South Texas Uranium Province is famous for its rollfront-type uranium deposits along oxidation-reduction boundaries. The Catahoula Formation is an ancient fluvial and volcanic mixtures forming a wide range of water/sediment interactions of the South Texas Coastal Plain. Tuffaceous volcanic deposits in Catahoula Formation are believed to be the main source of uranium. Uranium transport occurs in parts of the Catahoula aquifer in oxidizing and neutral to highly basic groundwater. Uranium deposits form along hydrologically active oxidation interfaces separating epigenetic sulfidic and epigenetic oxidation zones.

Conventional mining and milling were common for uranium recovery in Texas. Recently, in-situ leaching (ISL), a process that re-mobilize and recovers uranium, has been used. After ISL is complete, it is required to remove all radiological hazards and restore the groundwater of the now-depleted uranium capture zone back to pre-ISL conditions. Improper post-ISL can contaminate water and threaten public health in drinking water and other water usage. In addition, literature indicates that uranium mineralization occurs in many geological units below the water table that can be shallow (~90 feet) and can discharge to surface water bodies through faults or buried paleo-channels. Despite historical high uranium concentrations in many wells in South Texas, the demand for more water is increasing because population growth in Rio Grande Valley.

Our study area is Groundwater Management Area (GMA) 16 defined by Texas Water Development Board. Groundwater and surface water samples are being collected in many counties in GMA 16 including cities of Falfurrias, Hebbronville, Freer, and Kingsville.

Analysis of current data are in progress and additional data and water samples are being collected. Geochemical indicators will be examined for possible correlations. Portable X-ray fluorescence (pXRF) and X-ray diffraction (XRD) will be used to develop rapid screening technique. GIS spatial analysis will follow to analyze distributions/concentrations after water chemistry analysis.