The reality of sampling and assessing vapour intrusion on petroleum sites

Issues associated with vapour intrusion have been considered in Australia since the early 1990's; however, as there is no regulatory guidance, the sampling and assessment of vapour intrusion can be difficult. In addition, the need to collect sufficient data to enable an appropriate assessment of vapour intrusion, and resulting health risk has to be balanced against the limitations placed on the project by clients. Best practice guidance with respect to modelling, sampling and quantifying vapour intrusion is available from international sources; however, the reality of undertaking these assessments within such regulatory climates, as well as under client driven limitations, is challenging. Issues associated with the assessment of these sites are particularly evident when reviewing a wide range of petroleum related sites across Australia. The following paper provides a realistic review of 47 petroleum contaminated sites where vapour intrusion has been assessed on the basis of both modelling and the collection of site-specific data. The review presented identifies the key limitations on the data that have been collected on these sites, and whether these limitations are significant enough to affect the outcome and degree of uncertainty of the assessment. The review also evaluates whether the data collected are sufficiently robust to be critically assessed against current theories associated with the migration of petroleum hydrocarbon vapours in the subsurface and potential for vapour intrusion issues. The paper identifies the key aspects of vapour intrusion assessments that must be addressed, in any regulatory or client driven environment, to enable an adequate assessment of an issue where the ultimate goal is the protection of human health.