Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Dr. Jason Gerhard

2nd Supervisor

Dr. Panagiotis Tsourlos

Co-Supervisor

Abstract

Time-lapse Electrical Resistivity Tomography (ERT), a surface geophysical technique, was applied for the first time to monitor the first full-scale application of Self-sustaining Treatment for Active Remediation (STAR) at a coal tar contaminated site. STAR is a self-sustaining smouldering technology that destroys contaminants in situ by combustion, generating heat, water, and combustion gases. ERT is used as a complementary source of information to support conventional temperature and gas concentration data collected during STAR operations. A shallow (2.4 mbgs) and a deep (7.8 mbgs) treatment cell were monitored, with 2D surface resistivity surveys conducted before, during and after treatment. Two 36 electrodes lines were installed in each cell, with 21 meters of extension in the shallow and 42 meters in the deep cell. In the shallow cell, ERT identified a specific electrical resistivity signal based on temperature and water saturation changes to map the suspected coal tar treatment zones. In both cells, air/gas distribution was observed, as was the capture zone of the vapor extraction system and the re-infiltration of groundwater after treatment. The average subsurface resistivity presented the same trends as other measures of treatment, such as the total amount of combustion gases collected. Overall, the resistivity surveys provided continuous mapping of the subsurface, and showed that ERT is promising for evaluating thermal remediation field applications such as in situ STAR. This study represents the first time that in situ DNAPL remediation was mapped with ERT.

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