The U.S. Department of Energy (DOE) has initiated a Resource Conservation and Recovery Act (RCRA) Corrective Action process to address the impacts of past and potential future tank waste releases to the vadose zone at the 241-S-SX single-shell tank farms at the Hanford Site in southeastern Washington. The corrective actions include evaluation of impacts to groundwater resources (i.e., the concentration of contaminants in groundwater) and long-term risk to human health (associated with groundwater use). Numerical models have been developed that consider the extent of contamination presently within the vadose zone, contaminant movement through the vadose zone to groundwater, and contaminant movement in the groundwater to points of compliance. Results are included on analysis of laboratory measurements for physical and hydraulic properties for soil samples in the vicinity of the 241-S and 241-SX tank farms, and upscaling of small-scale measurements for soil moisture characteristics.