The purpose of this report is to first review the theory, operation, and potential applications of the tri-potential method of resistivity survey, and then to report on how this geophysical survey method was used at the Morgantown Energy Research Center's underground coal gasification (U.G.C.) site in Wetzel County, West Virginia; the results and conclusions from this phase of the project are also presented. This research project was performed under grant number GO155012 as funded by the U.S. Energy Research and Development Administration.