Vapor intrusion occurs due to volatile substances found in groundwater or soil, and they find their way into buildings inhabited by human beings. Vapor phase intrusion of the volatile substances is a threat to human health. The Pennsylvania Department of Environmental Protection (PADEP) provides guidelines and standards used for the evaluation of vapor intrusion under site-specific standard (SSS) and statewide health standard (SHS). Vapor intrusion transport is facilitated by the concentration gradient, temperature gradient and pressure gradient.
On January 18, 2017, PADEP adopted the “Land Recycling Program Technical Guidance Manual (TGM) for Vapor Intrusion into Buildings from Groundwater and Soil under Act 2”, which provides guidelines and standards for vapor intrusion in the state. It provides approaches for evaluating petroleum and non-petroleum products as well as further assessment options. The PADEP standards on vapor intrusion assessment involve the formulation of a Conceptual Site Model (CSM). The concentration of groundwater and soil volatile substance constituents are delineated. The Technical Guidance Manual (TGM) is then used to apply proximity distances to identify preferential pathways to facilitate the screening of potential vapor intrusion sources. Upon the identification of potential vapor intrusion pathways, any of the following options is applied: alternative vapor intrusion assessment options such as VI modelling, indoor air screening, sub-slab soil gas screening, and near-source soil gas screening; mitigation using an Environmental Covenant; remediation and re-evaluation of the vapor intrusion pathway; or the use of Act 2 site-specific standard (PADEP, n.d).
Vapor intrusion guidelines are suitable for constructors as they design buildings on specific sites. Factors considered include Significant Foundation Opening (SFO), Potential VI Source, Proximity Distance, Point of Application (POA), External Preferential Pathway, and Preferential Pathway. In general, vapor intrusion standards and guidelines protect human health by ensuring that people are protected from volatile substances found in soil and groundwater.
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PA Vapour Intrusion
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Reference
The Department of Environmental Protection, Pennsylvania (2021). Vapor Intrusion. Retrieved from https://www.dep.pa.gov/Business/Land/LandRecycling/Standards-Guidance-Procedures/Guidance-Technical-Tools/Pages/Vapor-Intrusion.aspx
