Tuesday, February 22, 2011

Vapor Intrusion Drifts Above the Contamination Landscape

by Duane Craig

What is Vapor Intrusion?

Vapor Intrusion illustration from the EPA
The contamination of the air by vapors is seeping into the news and the topic may be floating for some time to come. Called “vapor intrusion,” it is how chemicals travel from contaminated soil and water to the indoors.

Vapor Intrusion And The EPA

According to most accounts, it is a relatively new area of contamination study and the Environmental Protection Agency (EPA) is looking at it closely at the Havertown, Delaware, Superfund site.

The target there is trichloroethylene, which currently contaminates the groundwater and is thought to be potentially migrating as vapors into residences. The substance off-gases in soil and seeps into structures through cracks in foundations.

The EPA is also collecting comments on whether it should add vapor intrusion to the Hazard Ranking System used to place sites on its list requiring action. Once a process like vapor intrusion is allowed on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL), then sites with vapor intrusion evidence can be evaluated for placement on the list.
One of DuPont’s former munitions facilities near Pompton Lakes, New Jersey, might also make the list if vapor intrusion is allowed to be added. That site has a plume of contaminated ground water that extended beyond DuPont’s land and below 450 homes.

Read more about vapor intrusion here and here.

1 comment:

Anonymous said...

Actually, TCE and other VOCs, usually partition across the capillary fringe from groundwater in the vapor form, diffusing into the soil pore space by diffusion, and are then carried through the vadose zone, again by diffusion, in soil gas, which, based on the VOC concentration gradient across the vadose zone and the sub slab pressure differential, may then enter a building through cracks etc in the foundation slab, completing the VI pathway.