During Hanford Site operations, planned and unplanned releases of liquid wastes contaminated the underlying soils. This vadose zone (the area between the ground surface and the underlying water table) contamination spread vertically and horizontally, contaminating groundwater in several locations. For years, these groundwater plumes expanded and exhibited increasing constituent concentrations, indicating that contaminants were continuing to enter the groundwater from the vadose zone. The contaminated groundwater plumes are a key focus of current Hanford Site cleanup efforts, with several Pump and Treat facilities installed across the Hanford Site. While these Pump and Treat systems work to clean up the underlying groundwater, the Deep Vadose Zone project is focused on characterizing the remaining contamination within the Central Plateau vadose zone and identifying technologies to remediate soil and protect groundwater.

Since 2010, Freestone has provided the following support for the Hanford Site Deep Vadose Zone project: