Monitoring DNAPL pumping using integrated geophysical techniques
- Lawrence Livermore National Laboratory, CA (United States)
The removal of DNAPL during pumping has been monitored using integrated in situ geophysical techniques. At Hill Air Force Base in Utah, a free-product DNAPL plume (consisting predominantly of TCE) is pooled in water-wet soil on a thick clay aquitard. Groundwater pumping at Operable Unit 2 (OU 2) began in 1994; to date, nearly 30,000 gallons of DNAPL have been recovered from the site. From September, 1994 through September, 1995, changes in the basin during DNAPL pumping were monitored using an integrated geophysical system. Fiber optic sensors and neutron logs verify the presence of DNAPL in the vicinity of three boreholes which form a cross section from the perimeter of the basin to its center. Cross borehole electrical resistance tomography (ERT) images the changes in formation electrical properties due to the removal of DNAPL, extending the understanding of DNAPL removal between the boreholes. During pumping, electrical resistivities decreased; we suggest that these decreases are directly caused by the reduction in DNAPL. During ground water pumping, water with relatively low resistivity replaces some of the DNAPL pockets as the highly insulating DNAPL is removed. The results suggest that, as DNAPL is pumped from a nearby well, product slowly drains along the top of an aquitard and into the pump well, where it collects.
- OSTI ID:
- 381490
- Report Number(s):
- CONF-960477--
- Country of Publication:
- United States
- Language:
- English
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