Redwood City, California: GTR and C3 at a Former Dry Cleaner

GEO's Redwood City case study describes remediation at a former dry cleaner with PCE and lower concentrations of its degradation products. The approximately 384-square-foot target zone extended to 10 feet beneath the building. The remediation objective was based on vapor-intrusion risk and commercial soil-gas screening criteria.

Thermal remediation equipment inside the former dry cleaner in Redwood City, California.

The project combined Gas Thermal Remediation with C3 refrigerated vapor treatment. Nine thermal conduction heater wells with co-located vapor extraction were installed in three overlapping stages. Ten thermocouples and a central programmable logic controller supported heating control and monitoring. The target temperature was 100°C.

The English case study reports greater than 99.9% PCE and TCE removal from the vapor stream and greater than 99% reduction of PCE contamination in subsurface soil. Remediation goals were reached in 6.5 months, and the source reports that air-discharge requirements were met.

Contamination migrating from beneath a neighboring railroad line extended the heating period, illustrating the importance of defining treatment boundaries and nearby contaminant sources.