CROSS-WELL RADAR TO DETECT AND MONITOR DNAPLS

Contamination of soils and groundwater by Dense Non-Aqueous Phase Liquids (DNAPLs) causes serious detriment of the environment and can pose a serious threat to human health. These contaminants pose particular threats because of their heterogeneous distribution and long-term perseverance in the environment. Moreover, they are difficult to locate, characterize, and remediate. It is, therefore, necessary to develop new technologies that will enhance our ability to characterize contaminated sites, locate underground contaminants, evaluate fate and transport processes, and remediate these contaminated sites. More specifically, it is necessary to develop innovative non-invasive techniques that allow detection and monitoring of contaminants without disturbing the medium and promoting further spread of the pollutant.

The use of cross well radar (CWR) as a non-invasive technique has proven to be a reliable technology for detection of objects in soils under water saturated conditions. The CWR technology, however, must be further developed and tested for gradual distribution of DNAPL in unsaturated soils. The goal of this research is to develop and evaluate CWR technologies for detection and monitoring of DNAPL contaminants in unsaturated zone under transient conditions. Specifically, this study addresses the design and development of a 2D flow and electromagnetic soilBed, and the selection and design of the CWR antennas.

Preliminary work shows that a 2D electromagnetic field and DNAPL flow system requires metal plates in the soil Bed that are perpendicular to the transmitting signal but parallel to water and DNAPL flow lines. Parallel metal mesh plates are placed within the length of the soil Bed to simulate perfect electromagnetic reflection boundaries and allow continuous flow lines within the flow system. Stainless steel meshes of different aperture have been tested for these boundaries. Evaluation of different antennas suggest that loop antennas will be the most appropriate for the 2D system and will provide better response and resolution, and less scattering for the configuration of this flow system.