The INL (map below), under the jurisdiction of the U.S. Department of Energy (INL-DOE), includes a shallow-burial waste disposal site and other contaminated sites that contain a wide variety of radioactive and other hazardous wastes. Contaminants here are moving through a highly complex, 200-m deep unsaturated zone comprised of basalt flows interbedded with sediments. Processes involved in this transport are critical to the possible contamination of the intensely used Snake River Plain Aquifer. The Unsaturated-Zone Flow Project is conducting a long-term series of investigations of these processes, applying a combination of field observations and monitoring, field experiments, laboratory property measurements on core samples, theoretical developments, and numerical models. Our work at this site is in close collaboration with the INL Project of the Idaho District, and in cooperation with the DOE site management contractor.