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Hydrologic Characterization in the Vadose Zone at Hanford and Other Sites
Mobilized wastes leaking from tanks, cribs, and trenches are contaminating the groundwater at the Hanford Site. For example, technetium-99 was recently found in concentrations exceeding 80,000 pCi/L in groundwater near the 200 West SX-Tank farm. There is a clearly identified need to understand and quantify the flow and transport of wastes in the vadose zone and to use this information to predict the future groundwater contamination that could impact the Columbia River.
In an ongoing effort to meet this need, the U. S. Department of Energy Subsurface Contamination Focus Area (SUBCON) has funded the Pacific Northwest National Laboratory to deploy advanced monitoring systems that can be used to document the flow and transport of wastes in the vadose zone. New technologies with improved sensors allow better measures of the pressures and water contents in the vadose zone. In addition, improved and robust devices can be used to measure the vadose-zone water flux. Combining water-flux data with pressure profiles can provide improved estimates of the unsaturated hydraulic conductivity. Such information is currently lacking at most waste sites at Hanford and elsewhere.
The work reported on this web page provides a growing body of continuous data sets of hydrologic parameters (water pressure heads, water contents, and water fluxes) for the Hanford Site and for other selected sites around the United States where several of these sensor sets have been deployed. At some locations, thermal profiles are also being monitored. The data from these sites provide field-scale parameters for hydrologic modeling. The data also can be used to help resolve issues related to the impacts of meteoric water on groundwater recharge. Field sites, where hydrologic data are being collected, are identified below.