Preliminary Characterization Of A Napl-Contaminated Site Using Borehole Geophysical Techniques

We present preliminary results from an on-going geophysical investigation of the former DOE Pinellas<br>site, a site with confirmed non-aqueous phase liquid (NAPL) contamination. Our eventual goal<br>is the effective use of integrated crosswell geophysical methods, specifically seismic and radar tomography,<br>to remotely detect zones of high NAPL saturation. In this paper we discuss our motivation<br>and early efforts at using a combination of seismic and radar information to understand site geology<br>and possible contaminant signatures. We also present our current approach to consistent<br>acquisition, preprocessing, tomographic inversion, and interpretation of joint seismic/radar profiles.<br>Although direct geophysical evidence of NAPL pools has not yet been obtained, several regions of<br>anomalous seismic attenuation were detected. These attenuating regions could not be explained<br>by borehole effects or lithology and may be caused by regions of partial gas or NAPL saturation.<br>Possible gas sources include biogenic production from contaminated regions and side-effects from<br>previous remediation activities. Continuing research at the Pinellas site will focus on constraining<br>the mechanism responsible for the observed seismic attenuation, developing a more complete model<br>of site soil properties, and applying more quantitative approaches to the integration and analysis<br>of our seismic and radar images.