Vapor Intrusion – Challenges and Solutions

In December 2013, SERDP and ESTCP held a workshop on vapor intrusion to develop a strategic plan for investments addressing characterization and mitigation, as well as technology transfer. Specific questions addressed included:

  1. What additional research is warranted in this area, if any?
  2. Are there additional technology or methodology demonstrations needed to move the field forward to implementation of key concepts?
  3. What interactions need to take place with the end users?
  4. Are additional guidance documents, training, and/or seminars needed?

Approximately 25 invited experts representing DoD remedial program managers, state regulators, engineers, academic researchers, and consultants attended the workshop. A review of the research, demonstration, and technology transfer needs identified is presented in the workshop report.

Based on recommendations in the Workshop Report, ESTCP released a solicitation requesting proposals that addressed the development of methodologies, technologies or decision-making tools that could improve our ability to more accurately and cost effectively assess vapor intrusion from subsurface volatile organic compounds with the ultimate goal of providing better and more cost-effective protection of human health. Proposers were specifically asked to consider the following issues:

  • Impact of temporal and spatial variability of contaminant measurements on vapor intrusion assessments.
  • Impact of preferential vapor pathways on vapor intrusion assessments.
  • Identification of the lines of evidence required for a more accurate assessment of vapor intrusion.
  • Determination and management of the uncertainties associated with samples collected in the short term and their extrapolation over the long term.

Of particular interest was the development of an improved paradigm for assessing vapor intrusion that takes into account, but was not limited to, the issues listed above. ESTCP selected five projects under this solicitation.

Dr. Paul Johnson, at the Colorado School of Mines is leading an ESTCP project ( ER-201501) to demonstrate and validate a Vapor Intrusion Diagnosis Toolkit, using knowledge gained from previous SERDP and ESTCP funded vapor intrusion projects, for assessing vapor intrusion pathways and to mitigate impacts to buildings overlying contaminated groundwater plumes.

Dr. Thomas McHugh of GSI Environmental is currently studying the risk factors and investigation protocols of preferential pathways of sewers and utility tunnels for vapor migration from underlying plumes into buildings ( ER-201505). Dr. McHugh and his team will develop a protocol to determine the presence or absence of a sewer/utility tunnel preferential pathway develop a conceptual model for preferential pathways that identifies the types of sites at risk and the key mechanisms and processes involved in VOC transport through preferential pathways.

Another ESTCP project ( ER-201502) being led by Dr. Eric Suuberg at Brown University aims to demonstrate an advanced engineering modeling tool that could be made accessible to run on an ordinary desktop computer and user friendly enough to be used by personnel who are not familiar with advanced computation, in order to characterize vapor-impacted sites.

Dr. Helen Dawson’s team at Geosyntec is currently leading an ESTCP project ( ER-201503) to demonstrate mass flux characterization as a reliable and cost-effective approach to assess vapor intrusion that reduces the uncertainty associated with spatial and temporal variability in the concentrations of volatile organic compounds. Three different mass flux characterization methods are being evaluated.

A long term sampling approach is being developed by Dr. Alan Rossner and his team at Clarkson University ( ER-201504). The approach involves the use of evacuated canisters with a capillary flow controller over a period of 2 weeks for collection of VOCs. The new canister method captures the advantages of both canisters and sorbent samplers without their limitations by allowing for long-term (1-3 weeks) sample collection and characterization of VOCs in buildings at risk for vapor intrusion.

Summaries of the research and demonstration projects discussed above can be found on the SERDP and ESTCP web site. In addition, all reports originating from these efforts are available to download at the project web pages. Please contact the Environmental Restoration Program Manager if you have additional questions about this research area.

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