Environmental investigations at a former dry cleaning facility showed tetrachloroethylene (PCE) in sub-slab vapors exceeded its respective EPA target sub-slab vapor intrusion screening level (VISL). Based on the data, recommendations were made to the building owner to install a sub-slab mitigation system (VMS). A pilot test was conducted in the area where the former dry cleaning machine was located and a vacuum blower was then sized to affect an ROI needed to address the area of concern. A full-scale VMS was then designed and installed. After six weeks of operating the VMS, monitoring data showed non-detectable concentrations of PCE in the extracted vapors. The regulatory agency requested the VMS be turned off for one week and restarted. Analyses of the extracted vapors during startup showed PCE was greater than one order of magnitude lower than the EPA VISL. Based on the results, the agency cited that no further action was needed and issued a no further action approval to the client. This project shows the importance of conducting a pilot test for data to support the rationale for a VMS so that a system can effectively mitigate the vapors of concern.

Primary Author / Conference Presenter:
Robert Roth
Sr. Engineer
Wheat Ridge, Colorado, USA

Andy Safulko, Terracon, Wheat Ridge, Colorado, USA