Vapor Intrusion: Update on EPA’s Actions

On April 12, 2012, one of my colleagues, Dr. Khaled Chekiri, attended the “USEPA and Region V States Vapor Intrusion Video Conference Roundtable.”  The Video Conference was hosted by Barnes & Thornburg, LLP in their Grand Rapids, MI office. 

Some of the issues discussed included:

  • Decision making criteria for ruling VI in/out
  • Screening levels for contaminants with no published inhalation toxicity criteria (e.g., cis-1,2-DCE, MTBE)
  • Methane accumulation underneath buildings resulting from bioremediation of chlorinated compounds
  • Standard method recommended by EPA (sampling, leak detection)
  • The role of sub-slab pressure tests, indoor air tests; frequency of testing; the need for long-term monitoring
  • Vapor movement through soils and VI conducted in wetter climates with various soil regimes
  • Sub-slab testing protocols for large buildings (commercial/industrial settings)
  • Coordination with OSHA
  • Guidelines for dry cleaners who no longer use PCE (pick-up/drop off)
  • Criteria for requiring  installation of mitigation systems in residential and commercial settings
  • Discussion of radon mitigation system applicability to vapor mitigation
  • Long-term operation, maintenance, and monitoring guidelines for mitigation systems
  • Passive and long-term sampling
  • Decision making criteria when a VI mitigation system is no longer needed
  • Post-mitigation testing regime for a building

The United States Environmental Protection Agency (USEPA) stated they are still committed to November 2012 for final Vapor Intrusion (VI) guidance.  The guidance will address changes in toxicity values for PCE and TCE, mitigation methods, vapors related to petroleum hydrocarbons, and acceptable institutional controls.

Finally, a document that provides a conceptual model scenario for the VI Pathway is available for free download at http://www.epa.gov/oswer/vaporintrusion/.  The model may provide a “visual” help in determining the source location for various site conditions.  For example, the model shows that the distribution of petroleum compounds in soil gas can be very different from that of chlorinated compounds. 

This is just a brief overview of the four-hour conference.  If you have specific questions about VI, contact our Vice President of Technical Operations, Jeffrey Bolin, M.S., CHMM (jbolin@dragun.com) or Khaled Chekiri, Ph.D., P.E. (kchekiri@dragun.com) at 248-932-0228.

Please note: we continue to caution our clients to very carefully consider options before moving forward with any sampling related to assessing the potential impact of vapors.

For an overview of VI, see our March 2011 article in ESE “Vapour intrusion from soil and groundwater: A challenge for property owners”

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