Genna K. Olson

Short-Term TCE Risk Communication and Response

In 2019, the North Carolina Division of Waste Management (NC DWM) released supplemental vapor intrusion guidance detailing Immediate Action Levels (IALs) for trichloroethylene (TCE) in indoor air and steps needed to promptly eliminate or reduce the exposure for sensitive populations. This presentation will review case studies involving response actions to address detections of TCE above the IALs in indoor air. The policy requires notifications to building occupants regarding risks associated with indoor air concentrations, and staff from the NC DWM and the NC Department of Health and Human Services (NC DHHS) are typically involved in these notifications. The nature and timing of this sensitive risk communication to building occupants will be reviewed. Immediate mitigation measures performed to quickly reduce or eliminate exposure will also be reviewed, including indoor air treatment units, HVAC system adjustments, and vacating spaces. The presentation will review pros/cons, implementation details, and lessons learned associated with these immediate mitigation strategies. Methodologies for rapid assessment techniques successfully implemented to gather data needed for design of permanent mitigation measures will be discussed. Lastly, the presentation will review more permanent mitigation measures implemented, such as sub-slab and sub-membrane depressurization systems, as well as site-specific risk calculations performed in some cases to calculate alternate indoor air targets. Throughout, the presentation will focus on timing to rapidly achieve mitigation goals and eliminate exposures.