The ASTM Provisional Guide (PS 78–97) for Selecting Surface Geophysical Methods was developed as a guide for project managers, contractors, geologists, and geophysicists to assist in selecting the most likely geophysical method or methods to conduct specific subsurface investigations. Numerous surface geophysical methods and techniques exist that can be used to determine subsurface soil and rock properties and their distribution. These same methods are also widely used to investigate and locate manmade structures such as buried objects and landfills. This paper discusses the general uses of surface geophysics and the use of the provisional guide. This paper is not intended to be used as the guide. The ASTM Provisional Guide provides direction in selecting the most appropriate geophysical method or methods for a specific application under general site conditions. Secondary methods are also proposed that, under certain circumstances, should be evaluated before a final selection is made. Some typical conditions under which a primary or secondary method might or might not provide satisfactory results are given in the provisional guide. References for further information about selected methods and to method-specific ASTM guides are also provided. Secondary methods usually have less than desired performance, higher cost, or greater labor requirements as compared to the primary methods.

In latter 1979, approximately 200 drums of assorted waste chemicals were dumped in a rural area of southern New Jersey. The spill site is underlain by a water‐table aquifer which is the source of potable water throughout the general area. Emergency response personnel of the New Jersey Department of Environmental Protection (NJDEP) began a surface cleanup soon after the dumping, and requested Department geologists to investigate the dump site. An integrated approach combining drilling and sampling, downhole logging, surface resistivity, ground‐water conductivity and laboratory analyses for the common organic solvents was used to promptly assess ground‐water contamination and the controlling hydrogeology. Using routine hydrogeologic techniques and standard field equipment, within four months the emergency spill had been assessed by Department geologists and the outlines of a ground‐water decontamination program were evident.

Terrain conductivity is a geophysical technique which, by inducing current into the ground, can measure the conductivity of subsurface soils and interstitial waters. Hydrocarbons are not conductive materials and, because the surrounding lithology behaves to a certain extent as a conductor, the presence of pooled hydrocarbons floating on groundwater can be determined by the use of a terrain conductivity survey. Two case histories are presented in which terrain conductivity measurements were used to determine the extent and thickness of subsurface hydrocarbon plumes.

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