US EPA Releases Vapor Intrusion Guidance Document as Final

The US EPA released in June 2015 the Vapor Intrusion Guidance Document in its final version: OSWER Technical Guide for Assessing And Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air. In 2002, the EPA released the DRAFT version of the document which quickly became outdated as practices and knowledge rapidly developed in managing sites with vapor intrusion concerns.

The Final Guidance discusses the use of sorbent samplers in both the active and passive mode to measure soil gas and indoor air concentrations and includes references to two journal articles that published the results from studies performed by Beacon personnel. Of the numerous changes to the Final version, the recommended generic attenuation factor for sub-slab soil gas was changed from 0.1 to 0.03, which is still conservative but will provide a more reasonable estimation of a worst-case scenario.