input is presently derived from well log data, which may be scarce, especially in contaminated areas where drilling must be kept to a minimum. Seismic imaging pro-
vides a means to image the geo-
logic conditions between bore-
holes non-intrusively. Some of this imaging can be done with surface seismic data. However, placing both the source and receivers downhole results in shorter travel paths, which preserves higher seismic frequencies resulting in better resolution (Photo 1.4).

For remediation processes where the properties of the subsurface are changed (e.g., air sparging, steam flooding, or in situ vitrification), comparison of seismic velocity images before, during, and after the process can provide needed

information on where technology is being effective and to what degree the desired changes are being effected in the sub-surface.

Accomplishments

This technology has been success-
fully demonstrated at SRS. In addition to providing valuable data in the characterization of the geological conditions that existed prior to remedial activities, the method was also able to identify saturation changes associated with the in situ air stripping tests at the site. These changes in satu-
ration ranged from a few percent up to 22%. The spatial resolution of the present system is approxi-
mately 1 m in size and saturation changes of about 5% can be seen.