A survey of Department of Energy-sponsored geophysical research for shallow waste site characterization

Subsurface contamination plagues many USDOE sites and threatens groundwater supplies. This survey discusses research sponsored by the DOE Environmental Management Science Program (EMSP) for geophysical characterization of the vadose zone at the Idaho National Engineering and Environmental Laboratory (INEEL) and other contaminated sites. Various types of geophysical imaging techniques are used to characterize the shallow subsurface, including electromagnetic (EM), ground-penetrating radar (GPR), electrical, seismic, and nuclear magnetic resonance (NMR). Three common themes appear in the research surveyed in this article: (i) the development of high-resolution imaging capabilities to capture important details of the heterogeneous nature of subsurface properties and processes, (ii) the coupling of nonintrusive survey geophysical measurements (e.g., electrical surveys) with detailed quantitative precise point-sensor measurements (e.g., lysimeters and vapor-port systems) or borehole (e.g., NMR, neutron-based moisture, and geochemical tools) measurements to extend high-precision knowledge away from the borehole, and finally (iii) the application of multiple geophysical methods to constrain the uncertainty in determining critical subsurface physical properties. Laboratory, field, theoretical, and computational studies are necessary to develop our understanding of the manner in which contaminants travel through the vadose zone. Applications of geophysical methods to various contaminated areas at the INEEL are given.