An Ultra-Precise System for Electrical Resistivity Tomography Measurements

78301S One of the most widely used geophysical methods for monitoring flow within the shallow subsurface is Electrical Resistively Tomography (ERT). The latest generation of ERT systems can monitor data to a precision of around 1%, allowing in situ changes to be interpreted within a few percent. In turn, subsurface temperature changes can be monitored to within a few degrees Centigrade, low levels of tracers ¿ only slightly higher than background variations ¿ can be tracked, and fracture propagation on a site of several thousand square meters can be watched. This project would be to make the necessary improvements to hardware and data collection procedures that will push the current precision of ERT an additional order of magnitude. Phase I will investigate modifications to a number of interdependent systems and explore reductions in both random and systematic noise sources. Random noise will be reduced by implementing long data averaging periods (through the use of autonomous systems) and by improving stacking algorithms to address specific non-stationary noise problems (such as electrode corrosion). Systematic noise will be reduced by improving hardware design at several levels (including isolation of transmitter and receiver paths), improving calibration (using temperature stabilization and higher precision components), and identifying electrode materials that have more stable aging characteristics. Commercial Applications and Other Benefits as described by the awardee: The order-of-magnitude improvement in ERT measurement precision should enhance the overall effectiveness in existing monitoring applications without significantly increasing costs. The DOE complex alone has been estimated to contain 200 million cubic meters of contaminated soil (DOE, 1993), including those at the Hanford Reservation, the Savannah River Site, the Idaho National Environmental and Engineering Laboratory and the Nevada Test site.