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Earth Resistivity Surveys — A Method for Defining Ground‐Water Contamination a
Author(s) -
Stollar Robert L.,
Roux Paul
Publication year - 1975
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1975.tb03070.x
Subject(s) - groundwater , electrical resistivity and conductivity , contamination , pollution , earth (classical element) , natural (archaeology) , environmental science , geology , mining engineering , soil science , geotechnical engineering , engineering , ecology , physics , paleontology , electrical engineering , mathematical physics , biology
An important part of every investigation of ground‐water pollution is to locate and define the extent of the contaminated body of ground water. The usual method for accomplishing this is to install and sample numerous test wells, a costly and time‐consuming procedure. A much faster and less costly method, which has proven to give accurate results, is the earth resistivity survey. Because earth resistivity is inversely proportional to ground‐water conductivity, the location of ground water that has been contaminated by a relatively high concentration of conductive industrial wastes, for example, may be quickly and accurately traced. In order for the resistivity method to give useful results, resistivity contrasts must exist in the subsurface. For example, if the contaminant does not have a significantly greater conductivity than the natural ground water, or if the ground water is naturally highly conductive itself, a large enough resistivity contrast may not exist, and the method may not work. In addition, if depth to water is too great, the thickness of the unsaturated sediments can mask any contrasts between contaminated and natural ground water. The geologic environment must be relatively uniform so that the resistivity values and profiles can be compared with one another. At most industrial plant sites and landfills, these conditions are met. That is, the area of investigation is usually limited to a few hundred acres, where the geology and depth to water tend to be uniform. Four case histories of industrial and landfill sites are discussed in this paper. The areas underlain by the contaminated ground‐water bodies ranged from 25 to 100 acres. The depths to the contaminated water were relatively shallow, ranging from 5 to about 60 feet below land surface. In three of the cases, the results of the earth resistivity studies, which were verified by installing test wells in and around the area being investigated, proved to be remarkably accurate. In the fourth study, the conditions mentioned were not met, and the survey was unsuccessful.