Geoelectrical monitoring of dense non-aqueous phase liquid (DNAPL) remediation: Numerical, experimental, and field studies

Abstract

Effective remediation of brownfield sites contaminated with hazardous industrial chemicals – specifically dense non-aqueous phase liquids (DNAPLs) like coal tar, creosote and chlorinated solvents – remains a major geoenvironmental challenge. Remedial programs can benefit from geophysical methods to non-invasively map changes in the evolving DNAPL mass in space and time. Geoelectrical techniques have long exhibited strong potential in this context, but they are yet to become common tools at DNAPL sites. This presentation summarizes our recent numerical, laboratory and field work to assess the application of various geoelectrical methods for improved monitoring of DNAPL remediation. Novel couplings between a DNAPL model and geoelectrical models (e.g., GPR, ERT, TDIP) were developed to provide valuable and cost-effective exploratory tools for assessing the performance of GPR, ERT and TDIP for monitoring DNAPL remediation in complex, field-scale environments. Laboratory tank experiments were conducted to introduce a new surface-to-horizontal borehole configuration for improved ERT mapping of DNAPL remediation. At an industrial field site, ERT was used to successfully monitor a DNAPL source zone undergoing thermal remediation. Overall, this body of work demonstrates that geoelectrical techniques are indeed promising for mapping DNAPL remediation subject to some limitations and sometimes requiring innovative means of deployment, monitoring, and inversion.