GEOMORPHIC CONTROLS ON THE ENVIRONMENTAL FATE OF URANIUM - LUCKETT MINE, KARNES COUNTY, TEXAS

South Texas is an area in which extensive uranium mining has been conducted. Uranium was discovered in South Texas in 1954; uranium mining began in this region in 1960 and continued until the late 1980’s. The uranium ore was predominantly in the form of U3O8 found in sandstone roll front deposits. The host unit for the ore body is the Deweesville Sandstone, an upper Eocene barrier island sequence of fine-grained sands interbedded with silty clays (Rountree, et. al., 1987). The ore was extracted by shallow open pit mining. The environmental impacts of the mining include landscape degradation and the release of contaminants into the surface environment. Entrainment and transport of contaminants in this region occurs primarily during storms. Scared Dog Creek drains the mine site. This ephemeral creek has a catchment of approximately 15 km2 and drains into the San Antonio River with the confluence of these being approximately 7 km from the site of the Luckett Mine.

Our research is focused on the processes that control U dispersion in the catchment. Were concentrations decreasing exponentially or was there a linear decrease? How much sediment and associated contaminants were being entrained during storms? To answer these questions, both field and laboratory methods were employed. The entrainment of U in different geomorphic environments were established through characterization of soil and sediment cores taken from both reclaimed and unreclaimed areas including wetlands, creek channels, and the floodplain. Particle-mediated transport of U in this system was quantified through runoff and stream flow measurements taken following precipitation events and the analysis of water and suspended sediment samples. Uranium in all samples was quantified using voltammetry and ICP-MS.