This work is addressing the need to have accurate predictive models for transport in the vadose zone. Crosswell methods are aimed to provide a detailed understanding of how the physical properties ( layering, lithology, etc) affect the transport of fluids. Understanding of contaminant migration through the vadose zone has not only been hampered by inadequate conceptual models but has suffered from inadequate monitoring technologies. In the past, contaminant plumes at Hanford have most often mapped with gross and spectral gamma logging tools. Migration was documented by observing changes in gamma logs which failed to fully describe the contaminant plume since the dominant gamma emitters (e.g., 137Cs, 90Sr) are reactive and hence retarded in Hanford sediments, while non-reactive contaminants such as technetium, tritium, nitrate, move readily with the water. The inability to track highly mobile species through the vadose zone highlights an important need, the need for methods other than gamma logging to describe the complete vadose zone plume and to determine processes controlling accelerated contamination of groundwater at Hanford.
Revised: January 30, 2003 |
Published: July 1, 2001