Automated Time-lapse GPR Imaging of an Ethanol Release

The increased use of biofuels (e.g. ethanol) as an alternative to, and additive in, petroleum-based fuels likely will result in the same types of accidental releases and exposure currently associated with the transport and storage of petroleum products. Within the last decade a large number of studies have focused on the geophysical detection and monitoring of petroleum-based fuel releases, and subsequent biodegradation and remediation activity. Ethanol has unique properties; it is miscible in water, preferentially biodegraded, and manifests cosolvency when released in the presence of existing contamination. New tools are needed to rapidly identify and delineate a potential release to the subsurface. This study examines the feasibility of using ground penetrating radar (GPR) as a tool to image the migration of an ethanol release within an Ottawa sand matrix. A tank scale model of a closed hydrologic system was prepared. An automated gantry measurement apparatus allowed for both zero offset, and coincident reflection measurements with a multi-channel 800 MHz GPR system on multiple horizontal planes. Measurements were acquired in the vadose and saturated zones to image the injection and migration of the ethanol release. Preliminary results suggest a measureable contrast within the time series GPR data at the location of the injected ethanol release and subsequent migration.