Comparisons of IP and Resistivity Data at Several Old, Buried Landfills
Environmental and Engineering Geophysical Society (EEGS), 2004 Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP) proceedings.
Norman R. Carlson, Scott A. Urquhart, Zonge Engineering & Research Organization, Inc., Tucson, Arizona, U.S.A.
Paper – [pdf] ENV_ComparisonsOfIPandResistivityDataSAGEEP2004
While resistivity and conductivity continue to be two of the most common methods used for mapping old, buried landfills, we continue to encounter sites where the resistivity contrast between the landfill and the background material is either non-existent or inconsistent. Several recent examples are presented, including two landfill pits located just 2500 feet apart. Based on boring results, at one of the landfills both resistivity and induced polarization (IP) data
clearly delineated the waste boundaries, but at the other landfill, in the same geological background material, resistivity (and conductivity) failed to delineate the waste while there was a clear, well-defined correlation between IP effects and waste. The location and volume of waste would have been severely misjudged had we relied on resistivity or conductivity in advising the environmental firm tasked with evaluating the property.
Although IP effects were measured over a landfill thirty years ago (Angoran, et. al., 1974), IP surveys have not been applied regularly to landfill studies due to the difficulty and expense of acquiring good quality data. During this time, resistivity and its inverse, conductivity, and magnetics (in cases where significant amounts of ferrous metal are present) have been the traditional “tools of choice” for buried landfill mapping.
With improvements in field equipment and inversion modeling, however, during the last few years we have been able to acquire both resistivity and IP data at several dozen landfills during projects for various environmental firms and government entities. In this paper, we summarize several general results based on these surveys, with specific examples comparing resistivity and IP data.