HR: 0800h
AN: NS31B-0382    [Abstracts]
TI: Imaging Nuclear Waste Plumes at the Hanford Site using Large Domain 3D High Resolution Resistivity Methods and the New Parallel-Processing EarthImager3DCL Program
AU: Greenwood, J
EM: jgreenwood@hgiworld.com
AF: hydroGEOPHYSICS, Inc., 2302 N Forbes Blvd, Tucson, AZ 85745, United States
AU: * Rucker, D
EM: dale@ hydrogeophysics.com
AF: hydroGEOPHYSICS, Inc., 2302 N Forbes Blvd, Tucson, AZ 85745, United States
AU: Levitt, M
EM: marc@hydrogeophysics.com
AF: hydroGEOPHYSICS, Inc., 2302 N Forbes Blvd, Tucson, AZ 85745, United States
AU: Yang, X
EM: yang@agiusa.com
AF: Advanced Geosciences, Inc., 2121 Geoscience Dr., Austin, TX 78726, United States
AU: Lagmanson, M
EM: mats@agiusa.com
AF: Advanced Geosciences, Inc., 2121 Geoscience Dr., Austin, TX 78726, United States
AB: High Resolution Resistivity data is currently used by hydroGEOPHYSICS, Inc to detect and characterize the distribution of suspected contaminant plumes beneath leaking tanks and disposal sites within the U.S. Department of Energy Hanford Site, in Eastern Washington State. The success of the characterization effort has led to resistivity data acquisition in extremely large survey areas exceeding 0.6 km² and containing over 6,000 electrodes. Optimal data processing results are achieved by utilizing 10⁵ data points within a single finite difference or finite element model domain. The large number of measurements and electrodes and high resolution of the modeling domain requires a model mesh of over 10⁶ nodes. Existing commercially available resistivity inversion software could not support the domain size due to software and hardware limitations. hydroGEOPHYSICS, Inc teamed with Advanced Geosciences, Inc to advance the existing EarthImager3D inversion software to allow for parallel-processing and large memory support under a 64 bit operating system. The basis for the selection of EarthImager3D is demonstrated with a series of verification tests and benchmark comparisons using synthetic test models, field scale experiments and 6 months of intensive modeling using an array of multi-processor servers. The results of benchmark testing show equivalence to other industry standard inversion codes that perform the same function on significantly smaller domain models. hydroGEOPHYSICS, Inc included the use of 214 steel-cased monitoring wells as "long electrodes", 6000 surface electrodes and 8 buried point source electrodes. Advanced Geosciences, Inc. implemented a long electrode modeling function to support the Hanford Site well casing data. This utility is unique to commercial resistivity inversion software, and was evaluated through a series of laboratory and field scale tests using engineered subsurface plumes. The Hanford site is an ideal proving ground for these methods due to the large contrast in resistivity between contaminant plume (10 to 100 Ohm-m) and background soil (1000 to 1500 Ohm-m). The resulting improvements in hardware and inversion software radically increased the size of imaging domain and decreased processing time while allowing for a higher resolution three-dimensional visualization of possible subsurface contaminant plumes.
UR: http://www.hgiworld.com
DE: 0545 Modeling (4255)
DE: 0550 Model verification and validation
DE: 1835 Hydrogeophysics
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting