Tank Leak Detection Using Electrical Resistance Methods

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 paper provides a summary of the field experiments performed under a 15 m diameter steel tank mockup located at the Hanford Reservation, Washington. 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 show that, as the solution penetrated the soil, readily detectable resistivity decreases appeared where the associated plume was expected. The 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 is used as a large electrode.