On June 11, EPA released two long-awaited guidance documents on addressing the potential for vapor intrusion at contaminated sites. Vapor intrusion is the potential for vapors from groundwater contamination to enter occupied buildings. One guidance document, EPA’s “Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources,” applies to all sites being investigated under cleanup programs such as Superfund, RCRA corrective action, and state-led Superfund sites. It applies to contaminants other than petroleum, to mixed petroleum and other contaminant sites, and to petroleum contamination sites other than underground storage tanks (USTs). It can be found here. The other guidance, EPA’s Technical Guide for Addressing Petroleum Vapor Intrusion At Leaking Underground Storage Tank Sites,” applies to sites involving petroleum contamination from USTs, and can be found here.