1165420 - What’s New in Vapor Intrusion?

A significant environmental issue associated with sites contaminated with volatile organic compounds (VOCs) is vapor intrusion (VI) into nearby buildings. Residential homes, schools, and businesses may be located near sites where historical VOC releases to the subsurface have occurred. The potential for VI risk often drives stakeholder pressure for rigorous VI assessment and mitigation. However, the VI pathway from the subsurface to indoor air is complex and often misunderstood, potentially resulting in excess cost and time spent on an underperforming remedy. Technologies are emerging to more efficiently investigate and mitigate VI. When using traditional methods (e.g., pre-evacuated canisters), large amounts of data can be required to understand variability and fully assess VI. Collecting multiple rounds of canister samples of air and subslab vapor inside buildings may no longer provide the evidence regulators require. Newer techniques can assess VI more quickly while reducing uncertainty. These techniques can also resolve potential concerns associated with interference from background sources. This presentation provides a high-level overview of emerging techniques, including: 1) near real-time monitoring to obtain high resolution indoor air data, 2) building pressure control to assess temporal variability and identify VI entry points and/or background sources, 3) indicators to predict optimum times to sample, 4) tracers to aid in development of building specific attenuation factors, and 5) soil vapor extraction for VI mitigation. The presentation will go into more depth on the use of near real-time monitoring and soil vapor extraction for VI mitigation. Additionally, case studies will be presented for these two technologies that demonstrate how they can effectively mitigate VI over a large area, rapidly reduce risk, save costs, and accelerate the remedial process.