Brownfield Site Investigation Using Geophysics: A Case History From East Chicago

Abstract

Brownfields are areas in cities that have been determined to have environmental problems due to industry that once operated at those sites. At present, most of the areas are open tracts of land and they cannot be used or cleaned up until the extent of contamination has been determined. It has been suggested that geophysics be used to conduct non-invasive sit characterization. Urban areas have additional problems associated with then, including power line, rebar in concrete, electrical lines in buildings, and large metal objects near by that often interfere with electromagnetic (EM) and magnetic measurements. All of these aspects must be taken into account in designing an effective geophysical survey in an urban environment. A Brownfield site in East Chicago was used to demonstrate the effectiveness of utilizing geophysics and to develop strategies for applying geophysics to Brownfields. The site contained all of the problems listed above. Ground penetrating radar (GPR), multi-frequency EM measurements, and vertical and horizontal gradient measurements were made. Comparisons of the magnetic and EM measurements proved to make it easier to evaluate the GPR measurements at this site. This is the most extensive study to date of a comparison of geophysical methods in an urban setting. The comparison of methods indicate the following: (1) there needs to be very close (one foot or less) line and station spacing, (2) instruments should be run in orthogonal directions, and (3) multiple methods should be used for the best characterization of the sites.