Vapor intrusion (VI) refers to the movement of chemical vapors from contaminated soils or groundwater through the subsurface and into buildings (indoor air). This exposure pathway has attracted significant attention from regulatory agencies over the past decade in response to several well-publicized cases. Virtually all of the current regulatory documents generated are guidance and have not been promulgated as law, allowing for negotiation on the approach to follow in accordance to site-specific conditions. Nevertheless, experience indicates that this guidance also leads to higher costs in mitigation, public relations, and potential litigation. In response to the need for future research and development on reducing high costs and uncertainties of VI assessment strategies (Department of the Navy, DON, 2008), the objective of this report is to identify existing best practices, knowledge and data gaps, and future research into new strategies and techniques. This study was supported by the Navy Environmental Sustainability Development to Integration Program (NESDI) Program, as part of the study on Improved Strategies for Assessment of Vapor Intrusion, under direction by the Space and Naval Warfare (SPAWAR) Systems Center Pacific.

This handbook was developed by the Tri-Service Environmental Risk Assessment Work Group (TSERAWG) to serve as a resource for remedial project managers (RPMs) who may need to investigate the vapor intrusion pathway at Department of Defense (DoD) sites. The Tri-Services of the DoD include the Departments of the Air Force, Army, and Navy, with the Department of the Navy (DON) including both the Navy and the Marine Corps. This handbook was developed to support RPMs working on both active and closed Air Force, Army, Navy, and Marine Corps bases, as well as Formerly Used Defense Sites (FUDS). The handbook is intended to provide a general framework for conducting vapor intrusion investigations under the Defense Environmental Restoration Program (DERP). Both residential and occupational exposure scenarios are discussed since both groups can be affected by vapor intrusion.

For decades, scientists have propounded on the risks of vapor intrusion, the process by which contaminants present in soil and groundwater migrate, via volatilization, into buildings and affect indoor air quality. After years of deliberation, the United States Environmental Protection Agency (USEPA) has now added a vapor intrusion component to the Hazard Ranking System (HRS). The USEPA uses the HRS to evaluate whether a site warrants inclusion on the agency's National Priorities List (NPL) for Superfund sites. While the inclusion of vapor intrusion on the HRS is a positive, albeit overdue, development in Superfund law, how USEPA structures and implements the vapor intrusion component into the existing HRS will determine whether this new enhancement will actually prove to be protective of human health. First, this note will examine the concept of vapor intrusion. Included in this discussion will be a description of the contaminants at play, how vapors enter buildings, where vapor intrusion sites are located, what the human health risks are and, lastly what is done to mitigate the risks that vapor intrusion presents. The note will then discuss the importance that vapor intrusion plays in the Brownfields, Superfund and the LEED-certified building discussion and why vapor intrusion is often identified as an environmental justice issue. Next, the note will discuss many of the difficulties facing vapor intrusion regulation and the roadblocks that may have inhibited the promulgation of federal regulation earlier. I will then describe the different ways states have regulated vapor intrusion by assessing two enforcement mechanisms used by states in regulating sites where vapor intrusion may be an issue. First, I will evaluate how states initially assess vapor intrusion versus how states assess other more regulated exposure pathways (such as ingestion of contaminated drinking water). If there is some sort of ranking or prioritization of sites, what weight, if any, is given to sites where vapor intrusion is an issue? Secondly, I will look at what steps states take, or require potentially responsible parties or responsible parties to take, when vapor intrusion has been identified. Lastly, based on components of state regulation, I will propose a regulatory framework for addressing vapor intrusion.

This poster summarizes the current Washington State Department of Ecology guidelines for evaluating vapor intrusion at sites.