Vadose Zone Transport Field Study: 3D Casing Tomography and High Resolution Resistivity

Using a cluster of 18-meter-long steel casings as electrodes we have dynamically imaged, in three-dimensions, controlled injection events for both Columbia River water and sodium thiosulfate solutions. These results were part of the Vadose Zone Transport Field Study (VZTFS) performed at the Hanford Nuclear Reservation located in Richland, Washington under the direction of Pacific Northwest National Laboratory during the past two years. Several geophysical methods were evaluated during the VZTFS. Our responsibility included high resolution resistivity (HRR) and steel casing resistivity tomography (SCRT). Thirty-two, six-inch, steel casings arranged in a radial pattern allowed electrical resistivity measurements to be made using five different casing arrays including a single, “buried” electrode in the non-conducting injection well. Additional non-invasive electrical measurements were made using a 100-electrode surface array. All results are compared to neutron density data obtained in the same 32 casings.