Investigation of dominant hydrogeochemical processes influencing uranium transport in groundwater at a retired explosives test site - 15727

The Lawrence Livermore National Laboratory (LLNL) Site 300 facility was established in 1955 to support US weapons research and development. Open-air explosives tests, that used depleted uranium as a proxy, were conducted at the Building 812 site. Depleted uranium was released into the environment, eventually migrating into the underlying sandstone bedrock aquifer. At the site, groundwater concentrations of uranium exceed the California Maximum Contaminant Level of 20 pico-Curies per liter (pCi/L). However, the groundwater contaminant plume appears to attenuate within 60 meters of the contaminant source, beyond which no depleted uranium is observed. The goal of this research is to determine the processes (i.e., sorption to mineral surfaces, biotransformation, diffusion, dispersion, and mineral precipitation) controlling attenuation of uranium in local groundwater. (authors)