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ELECTRICAL RESISTIVITY VARIATIONS ASSOCIATED WITH CONTROLLED GASOLINE SPILLS
Citation:
Mazzella, A T. ELECTRICAL RESISTIVITY VARIATIONS ASSOCIATED WITH CONTROLLED GASOLINE SPILLS. Presented at 36th Annual Engineering Geology & Giotechnical Engineering Symposium, Las Vegas, NV, March 28-30, 2001.
Impact/Purpose:
Research is being conducted to improve and evaluate the resolution of the CR, EM, seismic, and GPR methods over complex geological formations (such as fractured geologies) and to evaluate the capability of these geophysical methods to delineate subsurface organic contaminants.
Description:
A number of geophysical surveys were conducted over two controlled releases of about 100 gallons each of gasoline. In order to clearly identify the responses associated with the gasoline plume, measurements were made before, during and after the injection. The two experiments were conducted about three years apart in the same geologic cell at the controlled tank facilities at the Oregon Graduate Institute in Beaverton , OR- The results of high resolution (2.5 cm spacing) downhole electrical resistivity measurements are presented in this paper.
An increase in the electrical resistivity, in the capillary zone above the water table was observed with the injected gasoline plume in both experiments. However, the magnitude and shape of the anomaly were considerably different in the two experiments and appear to be associated with the properties of the capillary zone and history of water infiltration prior to the gasoline injection In order to study longer term responses, measurements were taken 7 months Later m the second experiment. These results proved difficult to interpret because considerable rainfall in the area flooded the cell a number of times, causing movement and smearing of the gasoline plume.