Vapor Intrusion

GSI Environmental has been a leader in vapor intrusion for more than 10 years. We have lead the development and validation of innovative vapor intrusion investigation methods such as i) use of radon as a naturally-occurring tracer of soil gas migration into buildings, ii) pressure cycling (i.e., indoor air sampling under controlled building pressure conditions), and iii) use of compound-specific stable isotope analysis (CSIA) to distinguish between vapor intrusion and indoor sources of VOCs. In addition, we have developed improved vapor intrusion models including BioVapor, an analytical model for petroleum vapor intrusion that includes oxygen-limited aerobic biodegradation.

GSI Environmental conducts vapor intrusion investigations for industry clients, leads vapor intrusion research projects for the U.S. Department of Defense (including ESTCP, AFCEE, and NAVFAC), and participates in vapor intrusion workgroups organized by USEPA, ASTM, and state regulatory agencies.

Representative Experience

Vapor Intrusion Research Projects:

• Three-year DoD research project to develop improved vapor intrusion field investigation methods. Validated use of radon as a naturally-occurring tracer for the movement of soil gas into buildings. ESTCP Project ER-0423
• Four-year DoD research project to develop improved Tier 2 and Tier 3 vapor intrusion screening procedures. ESTCP Project ER-0707

Model Development:

• API BioVapor Software Tool: an analytical model for petroleum vapor intrusion that includes oxygen-limited aerobic biodegradation
• Mass flux model: A model of VOC transport from groundwater to indoor air that uses mass flux analyses to provide more realistic vapor intrusion predictions at sites with slower groundwater flow rates.

Site Investigation:

• Collected groundwater, soil gas, and indoor air samples to evaluate the potential for indoor air impacts associated with chlorinated solvents in groundwater under residential and commercial properties.
• Conducted comprehensive soil gas survey at former petroleum refinery to evaluate the potential for vapor intrusion following site redevelopment.

Workgroups and Guidance Documents:

• Developed vapor intrusion best practices guidance documents and web-based training program for industry client
• Participated in vapor intrusion workgroups organized by USEPA, ASTM, and state regulatory agencies
• Reviewed and commented on numerous guidance documents developed by the USEPA, state regulatory agencies, and stakeholder groups.

Vapor Intrusion Publications

McHugh T.E., McAlary, T., “Important Physical Processes For Vapor Intrusion: A Literature Review” in Proceedings of AWMA Vapor Intrusion Conference (San Diego, CA, January 28-30, 2009).

McHugh T.E., Hammond, D.E., Nickles, T., Hartman, B., “Use of Radon Measurements for Evaluation of VOC Vapor Intrusion”, Environmental Forensics, Vol. 9 No. 1, p. 107, March 2008.

McHugh T.E., Nickles, T.N., Brock, S., “Evaluation of Spatial and Temporal Variability in VOC Concentrations at Vapor Intrusion Investigation Sites” in Proceedings of Vapor Intrusion: Learning from the Challenges (Providence, RI, September 26-28, 2007).

Connor J.A., F. Ahmad, and T.E. McHugh. 2006. “Evaluation of Vapor Intrusion from Subsurface Diesel Plume Using Multiple Lines of Evidence”, Proceedings of Petroleum Hydrocarbons and Organic Chemicals in Ground Water: Prevention, Assessment, and Remediation Conference, Houston, Texas, 6-7 November 2006

McHugh, T.E., de Blanc, P.C., and Pokluda, R.J. “Indoor Air as a Source of VOC Contamination in Shallow Soils Below Buildings” Soil and Sed. Contam., Vol. 15, No. 1, pp. 103-122, January 2006.

McHugh, T.E. Ahmad, F. Connor, J.A. “Empirical Analysis of Groundwater-to-Indoor-Air Exposure Pathway Based on Measured Concentrations at Multiple Groundwater Impact Sites” Env. Forensics. Vol. 5, No. 1, pp. 33-44, March 2004.