Three-dimensional electrical resistivity model of a nuclear waste disposal site

Abstract A three-dimensional (3D) modeling study was completed on a very large electrical resistivity survey conducted at a nuclear waste site in eastern Washington. The acquisition included 47 pole–pole two-dimensional (2D) resistivity profiles collected along parallel and orthogonal lines over an area of 850 m × 570 m. The data were geo-referenced and inverted using EarthImager3D (EI3D). EI3D runs on a Microsoft 32-bit operating system (e.g. WIN-2K, XP) with a maximum usable memory of 2 GB. The memory limits the size of the domain for the inversion model to 200 m × 200 m, based on the survey electrode density. Therefore, a series of increasing overlapping models were run to evaluate the effectiveness of dividing the survey area into smaller subdomains. The results of the smaller subdomains were compared to the inversion results of a single domain over a larger area using an upgraded form of EI3D that incorporates multi-processing capabilities and 32 GB of RAM memory. The contours from the smaller subdomains showed discontinuity at the boundaries between the adjacent models, which do not match the hydrogeologic expectations given the nature of disposal at the site. At several boundaries, the contours of the low resistivity areas close, leaving the appearance of disconnected plumes or open contours at boundaries are not met with a continuance of the low resistivity plume into the adjacent subdomain. The model results of the single large domain show a continuous monolithic plume within the central and western portion of the site, directly beneath the elongated trenches. It is recommended that where possible, the domain not be subdivided, but instead include as much of the domain as possible given the memory of available computing resources.

[1]  T. Günther,et al.  Three‐dimensional modelling and inversion of dc resistivity data incorporating topography – II. Inversion , 2006 .

[2]  Philip I. Meldrum,et al.  3D resistivity imaging of buried oil- and tar-contaminated waste deposits , 1999 .

[3]  Duane G. Horton,et al.  Results of 1999 Spectral Gamma-Ray and Neutron Moisture Monitoring of Boreholes at Specific Retention Facilities in the 200 East Area, Hanford Site , 2000 .

[4]  Stephen K. Park,et al.  Inversion of pole-pole data for 3-D resistivity structure beneath arrays of electrodes , 1991 .

[5]  K. Lieser,et al.  Technetium in the Hydrosphere and in the Geosphere , 1987 .

[6]  E. C. Sullivan,et al.  Standardization of Borehole Data to Support Vadose Zone Flow and Transport Modeling , 2007 .

[7]  T. Dahlin,et al.  A 3-D resistivity investigation of a contaminated site at Lernacken, Sweden , 2002 .

[8]  L. Bentley,et al.  Two‐ and three‐dimensional electrical resistivity imaging at a heterogeneous remediation site , 2004 .

[9]  Jie Zhang,et al.  3-D resistivity forward modeling and inversion using conjugate gradients , 1995 .

[10]  A. Dey,et al.  Resistivity modelling for arbitrarily shaped two-dimensional structures , 1979 .

[11]  T. Günther,et al.  Three‐dimensional modelling and inversion of dc resistivity data incorporating topography – II. Inversion , 2006 .

[12]  S. Friedel,et al.  Investigation of a Tertiary maar structure using three-dimensional resistivity imaging , 1999 .

[13]  J. Chambers,et al.  Electrical resistivity tomography applied to geologic, hydrogeologic, and engineering investigations at a former waste-disposal site , 2006 .

[14]  Laurence R. Bentley,et al.  Resolution of 3-D Electrical Resistivity Images from Inversions of 2-D Orthogonal Lines , 2005 .

[15]  Partha S. Routh,et al.  Time-lapse ERT monitoring of an injection/withdrawal experiment , 2006 .

[16]  Dale F. Rucker,et al.  Inorganic Plume Delineation Using Surface High‐Resolution Electrical Resistivity at the BC Cribs and Trenches Site, Hanford , 2007 .

[17]  W. Daily,et al.  Cross-borehole resistivity tomography , 1991 .

[18]  Mark D. Freshley,et al.  Hanford Site Vadose Zone Studies: An Overview , 2007 .

[19]  J. E. Chambers,et al.  The Use of 3D Electrical Resistivity Tomography to Characterise Waste and Leachate Distribution within a Closed Landfill, Thriplow, UK , 2002 .

[20]  Mary J. S. Roth,et al.  Improved 3D pole‐dipole resistivity surveys using radial measurement pairs , 2005 .

[21]  J. B. Fink Inorganic Plume Delination using Surface High Resolution Electrical Resistivity at the BC Cribs and Trenches Site , 2007 .

[22]  A. Binley,et al.  A 3D ERT study of solute transport in a large experimental tank , 2002 .

[23]  Christian Bernstone,et al.  A Roll-Along Technique For 3D Resistivity Data Acquisition With Multi-Electrode Arrays , 1997 .

[24]  A. Dey,et al.  Resistivity modeling for arbitrarily shaped three-dimensional structures , 1979 .

[25]  G. J. Reece,et al.  3D resistivity inversion using 2D measurements of the electric field , 2001 .

[26]  S. Friedel,et al.  Investigation of a slope endangered by rainfall-induced landslides using 3D resistivity tomography and geotechnical testing , 2006 .

[27]  J. Chambers,et al.  Mineshaft imaging using surface and crosshole 3D electrical resistivity tomography: A case history from the East Pennine Coalfield, UK , 2007 .

[28]  W. Hogland,et al.  DC-resistivity mapping of internal landfill structures: two pre-excavation surveys , 2000 .

[29]  John C. Cripps,et al.  3D electrical imaging of known targets at a controlled environmental test site , 2002 .

[30]  A. Binley,et al.  Cross-hole electrical imaging of a controlled saline tracer injection , 2000 .

[31]  Andrew Binley,et al.  Applying petrophysical models to radar travel time and electrical resistivity tomograms: Resolution‐dependent limitations , 2005 .

[32]  Lee Slater,et al.  Aquatic electrical resistivity imaging of shallow-water wetlands , 2007 .

[33]  Kamini Singha,et al.  Effects of spatially variable resolution on field-scale estimates of tracer concentration from electrical inversions using Archie’s law , 2006 .

[34]  Kamini Singha,et al.  Geoelectrical inference of mass transfer parameters using temporal moments , 2008 .

[35]  Paul D. Thorne,et al.  Carbon Tetrachloride Flow and Transport in the Subsurface of the 216‐Z‐9 Trench at the Hanford Site , 2007 .

[36]  Seong-Jun Cho,et al.  Three‐dimensional imaging of subsurface structures using resistivity data , 2001 .

[37]  T. Dahlin,et al.  A comparison of the Gauss-Newton and quasi-Newton methods in resistivity imaging inversion , 2002 .

[38]  R. Barker,et al.  Practical techniques for 3D resistivity surveys and data inversion1 , 1996 .

[39]  W. Daily,et al.  The effects of noise on Occam's inversion of resistivity tomography data , 1996 .