Three-Dimensional Inversion of IP Data from the INEL Cold Test Pit

The Cold Test Pit (CTP) has been carefully constructed to simulate stored hazardous waste occurrences at the Idaho National Laboratory (INEL). An induced polarization (IP) survey of the CTP shows a very strong polarization anomaly and a modest resistivity response associated with the simulated waste. The data have been interpreted using a three-dimensional (3-D) inversion algorithm based on the simultaneous iterative reconstruction technique (SIRT) and finite difference forward modeling to form a subsurface model of complex resistivity. The edges of the waste zone are well resolved. Limited depth extent is recognized, though the bottom of the waste appears too deep. The intrinsic polarizability of the waste material has been estimated by means of a forward modeling experiment.