Two field experiments were performed to evaluate the performance of electrical resistance tomography (ERT) as a leak detection method under metal underground storage tanks (UST). This document provides a summary of field experiment results performed under a 15 m diameter steel tank mockup located at the Hanford Reservation, Washington, and of supporting numerical simulations. Two different leak events were created. About 3800 liters of saline solution were first released along a portion of the tank's edge and another 1900 liters were later released near the tank's center. The release rate averaged about 26 liters/hour for the leak on the tank's side and about 3.0 liters/hour for the center leak. Two- and three-dimensional tomographs were calculated using data collected before, during and after each spill. The tomographs mapped the spatial and temporal evolution of resistivity changes caused by the leak; as the solution penetrated the soil, readily detectable resistivity decreases were observed and used to map the associated plume. The results show that the metal tank has significant effects on the results obtained, primarily in reducing sensitivity to the leak. The field results indicate that the plume associated with these releases could be reliably detected after approximately 190 liters were released. Results are also shown where the metal tank and metal-cased boreholes are used as large electrodes. We use the field results to extrapolate how these techniques could be used to detect and locate leaks, and to delineate any resulting plumes from the underground storage tanks.
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Ramirez et al. (1996) studied this question.