A Hybrid Hydrologic-Geophysical Inverse Technique For The Assessment And Monitoring Of Leachates In The Vadose Zone
At many DOE facilities, the presence of radioactive wastes and other contaminants within the vadose zone poses a serious and ongoing threat to public health and safety. In many cases these contaminants have been introduced directly to the vadose zone through releases on the surface or in shallow pits, and through leaking storage facilities. To reduce the environmental risks these wastes pose, the DOE is currently considering two fundamentally different approaches. The first involves remediation by treating contaminants in-place while the second, and more economically feasible being examined by DOE, involves in-situ immobilization of the wastes. Immobilization would be achieved through both injection of subsurface grout barriers to block transport pathways and installation of surface caps to prevent additional water infiltration into contaminated formations. A necessary requirement of both remediation approaches is the need to obtain information on the spatial distributions of the hydraulic and transport properties, the amount of contamination in place, and flow and transport processes that are occurring. With this information in hand, informed decisions can be made in order to optimize the remediation process for each particular case. In particular, these capabilities could result in reduced remediation costs, as well as providing necessary data to illustrate regulatory compliance. To reach these goals, existing monitoring technologies need to be improved and innovative technologies need to be developed to measure the spatial distribution of, and the temporal changes in moisture contents and contaminant concentrations within the vadose zone. The primary objective of the funded research addressed these needs through the development and field-testing of a Hybrid Hydrologic-Geophysical Inverse Technique (HHGIT). The resulting technology provides the ability to both monitor the evolution of certain types of contaminant plumes, and to characterize hydrologic properties within the vadose zone at contaminated sites. The HHGIT combines geophysical measurements such as electrical resistivity tomography (ERT), cross borehole ground penetrating radar (XBGPR), neutron moisture logs, sparse hydrologic data, and geostatistical information on the geologic heterogeneity to provide 2- and 3-D of moisture and hydrologic property distributions. By linking these three types of information into a single inversion, much better estimates of spatially varying hydraulic properties can be obtained than could be from interpreting the data types individually. Because the method is a geostatistically based estimation technique, the estimates represent conditional mean hydraulic property fields. Thus, this method quantifies the uncertainty of the estimates as well as the estimates themselves.
- Research Organization:
- University of Wisconsin, Madison (US)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM) (US)
- OSTI ID:
- 828251
- Report Number(s):
- EMSP-55332-2000; R&D Project: EMSP 55332; TRN: US0404262
- Resource Relation:
- Other Information: PBD: 31 Dec 2000
- Country of Publication:
- United States
- Language:
- English
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A hybrid hydrologic-geophysical inverse technique for the assessment and monitoring of leachates in the vadose zone. 1998 annual progress report
Related Subjects
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
CONTAMINATION
ELECTRIC CONDUCTIVITY
GROUTING
HYDRAULICS
LEACHATES
MOISTURE
MONITORING
NEUTRONS
PLUMES
PUBLIC HEALTH
RADAR
RADIOACTIVE WASTES
SAFETY
SPATIAL DISTRIBUTION
STORAGE FACILITIES
TOMOGRAPHY
WATER INFLUX