INTEGRATION OF GEOPHYSICAL INVESTIGATIONS OF THE TOOELE ARMY DEPOT (TEAD), TOOELE, UTAH

Abstract

Migrating, contaminated groundwater plumes continue to be a problem around the world. Over the last decade geophysical investigations have been performed to determine the depth to bedrock and fault structures at the Tooele Army Depot (TEAD) in support of development of a groundwater model. Borehole, seismic, time-domain electromagnetic, gravity, and audio-magnetotelluric surveys have been performed. As the investigations progressed, inconsistencies became apparent between the interpretations. Portions of some of the surveys became essentially useless to the Department of Defense client because they couldn’t be “trusted”. The geophysical results, processing, and interpretation for the different systems have been revisited and the results integrated into one interpretation. In the end, site survey coverage, relative to the complex local geology was determined to be the main issue and not geophysical data acquisition and interpretation. The complicated and rapidly varying geology at the site prevents full continuity of the geophysical interpretation of faulted blocks between the different lines and stations. A case is made for “wide-area” airborne electromagnetic and magnetic surveys of the Depot that would result in a more comprehensive data set and interpretation of the subsurface geology and groundwater flow in the TEAD area. This study reiterates that, in complicated areas, no single technique can stand on its own nor be interpreted in isolation. A suite of geophysical techniques must be applied and integrated into one interpretation.