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The contamination at the Idaho Nuclear Technology and Engineering Center (INTEC), like at other DOE contaminated vadose zone sites, resulted from the inadvertent discharge of extreme pH solutions contaminated with radionuclides and other toxic materials. The movement of these solutions and their interactions with subsurface media are poorly understood. As a result, overly conservative values of transport parameters are used to assess risk and evaluate cleanup options. Because actual remediation of the INTEC vadose zone is decades away, the results of long-term research can be fully implemented into future cleanup activities. In addition, because of the long time frame until remediation, interim monitoring of water and contaminant movement is needed.

Research focused on developing improved methods for vadose zone characterization and monitoring will be conducted at INTEC and satellite sites. The objectives of this research are to develop new point sensors that measure vadose state variables in near real time and to couple these observations with new high-resolution geophysical techniques to develop an integrated view of the subsurface and the movement of water through the subsurface. Of particular interest are the sediment-basalt interfaces and the physical processes that result in water ponding at these interfaces and its subsequent movement into the underlying fractured media. The generation, nature, and transport of colloids by extreme pH fluids are also of interest. In addition to sensor development and field observations, it is likely that the physics of fluid flow and colloid transport will be investigated using emerging techniques developed for geocentrifuges. Initial analysis suggests that vadose zone thickness and travel times scale in accordance to 1/g and 1/g², respectively, where g is the gravitational acceleration developed in the centrifuge. Such results may better elucidate the water travel times through the complex INL vadose zone than currently used modeling approaches.