'GROUNDWATER-PROPELLED' VAPOR INTRUSION: A NEW HEALTH HAZARD ?

Vapor intrusion (VI) of chlorinated hydrocarbons is a significant safety concern in areas overlying TCE and petroleum spills. Currently assessment is carried out by ranking sites for physical factors to determine if VI is present followed by modeling and sampling in basements. These approaches do not consider seasonal variations in water table. Furthermore, models used to predict VI parameterize it as a mixed advection and diffusion-controlled process from a fixed water table. In New York State there exist numerous spills of TCE and petroleum in the Onondaga FM. This unit has a history of dynamic water table variations. Underlying one of these dynamic areas, near Leroy, New York, is a TCE plume that is currently being characterized for VI. Well data indicate that water tables may rise between 20 and 50 feet in one day at this site. Wells at widely separated locations show similar fluctuations, implying these shifts in are regional phenomenon, rather than the result of unique sets of local geological conditions. These shifts commonly occur in the early spring when soils are frozen and when house ventilation is minimized for winter heating. It is hypothesized that water table rises may impact vapor intrusion by acting as a piston, forcing contaminated vapors into basements. This poster discusses the implications of dynamic water behavior in the context of VI protocols and presents evidence that this sort of water table behavior is present throughout the Onondaga FM, a lithologic unit that stretches across the entire state.