Patricia OvermeyerU.S. EPA/Office of Brownfields and Land Revitalization
Vapor intrusion generally occurs when there is a migration of volatile chemicals from contaminated groundwater or soil into an overlying building.Volatile chemicals can emit vapors that may migrate through subsurface soils and into indoor air spaces of overlying buildings in ways similar to that of radon gas seeping into homes.Volatile chemicals may include volatile organic compounds, select semivolatile organic compounds, and some inorganic analytes, such as elemental mercury, radon, and hydrogen sulfide.
All Appropriate Inquiries Rule Identify conditions indicative of releases or threatened releases of hazardous substances. (40 CFR 312.1(c))ASTM E1527-05 Identify recognized environmental conditions – or the presence or likely presence of any hazardous substances or petroleum products on a property under conditions that indicate an existing release, a past release or a material threat of a release…into structures on the property or inot the ground, ground water, or surface water….
A Phase I Site Assessment (or AAI Investigation) is not intended to: • Verify or document a specific release • Verify or document the presence of specific contamination • Document a specific source of a potential release • Document the extent of a release
Conditions indicative of a release that could result in vapor intrusion, or Presence or likely presence under conditions that indicate… a release that could lead to vapor intrusion Could be: ◦ Presence of USTs containing hydrocarbons ◦ Documentation of hydrocarbon releases at a nearby property
Goal of Phase I / AAI is not: ◦ To determine the presence of vapor intrusion (or the presence of any other release or result of a release) ◦ Document the presence of vapors or document vapor intrusion events
Updating EPA’s 2002 Draft Guidance on Subsurface Vapor Intrusion Developing guidance on petroleum vapor intrusion Hazardous Ranking System (HRS) Rulemaking Developing technical documents and tools
Planning to issue final Subsurface Vapor Intrusion Guidance by November 30, 2012. A request for public input was announced in the Federal Register on March 17, 2011 (76 FR 14660). Comment period ended on May 14, 2011, all comments received will be considered in developing the final guidance. Comments can be viewed at Regulations.gov (EPA-HQ- RCRA-2002-0033).
Petroleum hydrocarbons and chlorinated hydrocarbons behave differently in respect to VI pathway. The guidance will focus on federally‐regulated (Subtitle I) UST sites, which are typically gas stations. The guidance will contain information and practices that will be useful at other sites (e.g., fuel terminals and airport hydrant systems) where petroleum contamination is of potential concern.
EPA is working toward a proposed rulemaking to add a new screening component to OSWERs Hazard Ranking System (HRS). Would allow sites impacted by vapor intrusion or intrusion of other subsurface contamination to be evaluated for placement on the Superfund National Priorities List (NPL). Through this change, the HRS could directly consider the human exposure to contaminants that enter building structures from the subsurface environment.
The Brownfields and Land Revitalization Technology Support Center published Brownfields Technology Primer: Vapor Intrusion Considerations for Redevelopment. ◦ Provides an overview of vapor intrusion and how it can affect redevelopment. ◦ Summarizes techniques for quickly and cost effectively assessing the potential for vapor intrusion.
Background Indoor Air Concentrations of Volatile Organic Compounds in North American Residences (1990 – 2005): A Compilation of Statistics for Assessing Vapor Intrusion ◦ Summary of indoor air studies that measured background concentrations of VOCs in the indoor air of thousands of North American residences and an evaluation and compilation of the statistical information reported in these studies. ◦ Illustrates ranges and variability of VOC concentrations in indoor air resulting from sources other than vapor intrusion.
EPAs Vapor Intrusion Database: Evaluation and Characterization of Attenuation Factors for Chlorinated Volatile Organic Compounds and Residential Buildings Conceptual Model Scenarios for the Vapor Intrusion Pathway