Petroleum Vapor Intrusion

Abstract

AbstractPetroleum vapor intrusion (PVI) is the process by which volatile petroleum hydrocarbons released from contaminated geological materials or groundwater migrate through the vadose zone into overlying buildings. PVI science showed that petroleum hydrocarbons are subjected to natural attenuation processes in the source zone and during the vapor transport through the vadose zone. Specifically, in the presence of oxygen, aerobic biodegradation typically reduces or eliminates the potential for PVI. This behavior justifies the different approach usually adopted for addressing PVI compared to less biodegradable compounds such as chlorinated solvents. In some countries, it was introduced the concept of vertical exclusion distance criteria, i.e., source to building distances above which PVI does not normally pose a concern. For buildings where the vertical separation distance does not meet screening criteria, additional assessment of the potential for PVI is necessary. These further investigations can be based on modeling of vapor intrusion, soil gas sampling, indoor measurements or preferably a combination of these to derive multiple lines of evidence. The data collected are then used for a risk assessment of the vapor intrusion pathway. This chapter provides an overview of state-of-the-science methodologies, models, benefits and drawbacks of current approaches, and recommendations for improvement.