Effective this month, the NJDEP has updated its vapor intrusion guidance. Vapor intrusion or “VI” refers to hazardous substances in contaminated soil or groundwater that may volatilize (i.e., disperse as a gas) and migrate upward through subsurface soils or other pathways and impact the indoor air quality of overlying buildings. Depending on the extent of hazardous substances present in the sub-slab or indoor air of a building, a responsible party may be required to monitor and/or mitigate the vapor intrusion pathway. Where levels of vapor intrusion exceed applicable standards, it may present an “immediate environmental concern” requiring rapid action. Site owners/operators should be sensitive to the changes in VI requirements, which apply to ongoing cleanup sites. More information is available at the NJDEP vapor intrusion website or by contacting a member of our environmental law team.