Vapor intrusion is the general term given to migration of hazardous vapors from any subsurface contaminant source, through the vadose zone and into indoor air. Vapor intrusion is widely recognized as a potentially significant cause of human exposure to volatile hazardous chemicals in indoor spaces.

Earth Systems, along with one other consulting firm, designed and implemented FDEP’s first vapor intrusion (VI) study. The study consisted of installing various types of vapor sampling probes near building foundations and through building slabs at eight facilities located throughout Florida to evaluate whether vapors could potentially accumulate around and beneath buildings located near documented hydrocarbon releases.

The VI data was evaluated to predict whether vapor intrusion beneath (or within) building structures located near impacted sites was a concern in Florida. Results of the various sampling events were evaluated to determine whether geotechnical properties of the soil, hydrocarbon concentrations in the soil, and dissolved hydrocarbons in the groundwater correlated with elevated hydrocarbon vapor concentrations in the vadose-zone soils and beneath building slabs. The sampling protocol was also evaluated to determine whether modifications should be implemented to improve the quality of the VI data.

Multiple factors can influence the potential indoor air concentration arising from vapor intrusion. Therefore, Earth Systems recommends collecting and evaluating multiple lines of evidence to characterize the vapor intrusion pathway and support risk management decisions.