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Identifying and Evaluating Vapor Intrusion through Preferential Migration Routes and Points of Entry into Buildings
Citation:
Schumacher, B., A. Lee, M. Plate, L. Abreu, J. Zimmerman, AND A. Williams. Identifying and Evaluating Vapor Intrusion through Preferential Migration Routes and Points of Entry into Buildings. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-21/272, 2021.
Impact/Purpose:
The project identified multiple methods to more easily and rapidly identify and mitigate preferential pathways into buildings. With these methods and tools, real-time measurements can be made and improved identification of buildings where vapor intrusion is occurring is possible such that mitigation measures can be undertaken to reduce or eliminate the exposure of the building inhabitants to the harmful volatile chemicals.
Description:
Vapor intrusion (VI) is the migration of hazardous vapors from a subsurface contaminant source into an overlying building or structure via any opening or conduit. Certain chemicals that are released into the subsurface may form hazardous vapors that migrate through the vadose zone and eventually enter buildings transported through direct openings and conduits such as cracks, seams, foundations, sump pits, utility vaults, floor drains and sewer lines. The role of preferential pathways for vapor intrusion is poorly understood and only recently, come to light as potential major transport route of volatile organic compounds (VOCs) into homes and buildings. A preferential pathway is typically defined as a high permeability conduit that can serve as a high-capacity transport pathway for VOC vapors from the source area to or into a building. Sewers or utility tunnels are of greatest concern when they pass directly through contaminated groundwater or vadose zone non-aqueous phase liquid (NAPL) sources since those locations could provide the highest concentration infiltration into the conduit. The overall objective of this research effort was to identify methods to evaluate potential preferential migration routes and points of entry into building space and assess the effectiveness of easily implementable field mitigation measures. To meet this goal the project team identified and used screening methods and tools (e.g., low cost testing of tracers and field portable sensors or meters) to rapidly identify preferential migration routes and points of vapor entry to the indoor environment. For a selected set of pathways, the research effort identified and tested the effectiveness of simple, easily implementable mitigation measures taken to minimize or prevent potential exposure from preferential migration routes and vapor intrusion points of entry into the building.