Monitoring of in situ remediation with the direct current time-domain induced polarization method

In Alingsås, a dry-cleaning facility was operated for many years, and huge amounts of the solvent PCE was spilled into the ground. This contributed to an increasing concentration of PCE over the years until the use of PCE was stopped, resulting in the formation of a DNAPL plume beneath the building. Treatment of contaminated soils in Sweden often includes excavation and landfilling, however in Alingsås this is not applicable. In situ remediation methods (thermal, biological, chemical) are the only alternative however, there is a need for tools to monitor the effectiveness of those methods. One method of particular interest in this context is the Direct Current time-domain Induced Polarization (DCIP). For that purpose, a fully autonomous and automatic monitoring system was installed in Alingsås, to perform frequent automated measurements and to provide information about the changes in the subsurface. The geophysical data should be ideally acquired, analyzed and verified with automated routines as part of a larger monitoring system. It is of great importance, especially in the early stage, to verify events that appear to show interesting changes with sampling data to evaluate the level of reliability of the system.