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Field Testing Soil Gas [Vapor] Safe Communities
Citation:
Schuver, H., B. Schumacher, J. Zimmerman, AND A. Williams. Field Testing Soil Gas [Vapor] Safe Communities. 2022 Association of Vapor Intrusion Professionals Conference, Nashville, TN, October 09 - 11, 2022.
Impact/Purpose:
Sample timing matters for both long-term average/chronic exposures (because the majority of chemical exposure can occur in a small fraction of the time), and it is even more important for shorter periods of exposure concern (e.g., for as little as one day for developmental toxicants such as trichloroethylene). The presentation will summarize the physical evidence of an association between Rn and chemical VI from highly studied buildings across the USA. These studies allow us to ‘target’ chemical sampling times and have led us to examine these ‘random’ versus ‘targeted’ sampling comparison field tests. We anticipate the communities in these field tests will understand and appreciate the benefits of ‘targeted’ sampling as well as the benefits of earlier exposure reductions in cases where the chemical contaminants are found immediately outside their building, and their own building measurements show that soil gas is intruding. We also anticipate the Potentially Responsible Parties/Decision-Makers, and other stakeholders, will appreciate the economic benefits of less indoor chemical-exposure-confirmatory sampling and the benefits of sooner and more confident elimination of VI exposure by ‘cutting off’ the soil gas intrusion pathway in these probably ‘unacceptable’ VI scenarios. In summary, this presentation will highlight how the SGSC approach could be an important part of the ‘Future of VI’ by providing benefits to all parties willing to lower the level of confidence needed to consider soil gas/VI risks as ‘unacceptable’ and to increase the confidence of protection by earlier and continuously verifiable long-term control of soil gas intrusion.
Description:
Background/Objectives. Soil gas intruding into homes and buildings has always been a detriment to indoor air quality (e.g., radon, CO2, moisture/mold) and it is getting worse (e.g., from spills of petroleum, chlorinated and perfluorinated chemicals). Despite several decades of effort, and largely due to both spatial (building-specific) and log-scale temporal variability, the assessment of chemical vapor intrusion (VI) exposures remains challenging, time consuming, expensive and provides results with limited confidence for representing exposure distributions. The USEPA’s contaminated sites cleanup programs and the Office of Research and Development (ORD) are working towards an objective of improving the accuracy and cost-effectiveness of future chemical vapor intrusion assessment, and the management of intruding soil gases including vapors, over the long-term.Approach/Activities. The USEPA is beginning to field test an approach, called Soil Gas [Vapor] Safe Communities (SGSC), that involves working closely with communities ‘at risk’ of chemical vapor intrusion to help participating community members document the intrusion of soil gas (possibly including chemical vapors) into their indoor air. The approach focuses on low-cost, high frequency, easily implemented measurements of a common component of soil gas, radon (Rn), as a tracer of soil gas intrusion, and supported by indicators of VI such as differential temperature and pressure. These indicators and tracers help identify the buildings most “at risk” and the best times to sample indoor air to document the reasonable maximum exposures (RME). ORD will be conducting these field tests at two site/communities with approximately 30 buildings each. Buildings with documented soil gas VI source immediately surrounding them will, with community members participation, undergo indoor air chemical sampling, at both typical ‘random/seasonal’ times and at ‘targeted’ times when the tracer Rn and/or indicators, suggest VI is ‘turned on’.