Background/Objectives

Approximately 25 years ago, indoor air testing began in residences near the Redfield site in Denver, Colorado. The detection of elevated concentrations of 1,1-DCE and other VOCs in these indoor air samples received widespread attention and initiated a more systematic evaluation of the vapor intrusion pathway at other VOC-contaminated sites. Testing at other sites soon demonstrated that the vapor intrusion pathway was a complete exposure pathway at many of these sites. In fact, vapor intrusion is likely the most common mechanism for actual exposure to VOCs across sites with subsurface VOC contamination.

Approach/Activities

This panel will be comprised of five or six vapor intrusion experts each with 20+ years of experience. This will include David Folkes, the lead consultant for the Redfield site, and Helen Dawson, who was with USEPA Region 8 in Denver at the time and was lead technical author for the 2002 USEPA Vapor Intrusion Guidance. Based on their experience, the panelists will be able to provide unique insights into the past, present, and future of this important exposure pathway.

Results/Lessons Learned

Other the past 25 years, our understanding of vapor intrusion has evolved dramatically. These changes are reflected in hundreds of peer-reviewed publications and regulatory guidance documents on vapor intrusion that document pathway screening procedures, investigation approaches, and mitigation methods. Despite these advances, evaluation of vapor intrusion remains challenging at many sites. No single vapor intrusion site screening and investigation approach has gained widespread acceptance; disagreements over pathway completeness are common; and fully characterizing spatial and temporal variability is difficult.

For this panel session, the panelists will briefly review the past 25 years of the vapor intrusion pathway, evaluate lessons learned, and discuss future opportunities to address the on-going challenges of the pathway.