Helen served as principal investigator for this project, which demonstrates three complementary, building-scale approaches: diffusive soil flux, building pressure cycling, and sub-slab venting. The report, published in May 2025, recently became available online.
Coauthors of the report were Daniel Carr of D. B. Carr Consulting, Theresa Gabris of Geo-Technology Associates, Inc., and William Wertz.
Helen is a Senior Principal Civil and Environmental Consultant based in Washington, DC, with more than 30 years of experience in the evaluation of complex contaminated sites. Her practice spans disciplines, including vapor intrusion, groundwater characterization, and contaminant fate and transport modeling related to the spread of dense nonaqueous-phase liquids, chlorinated solvents, and metals in the environment. A recognized leader in vapor intrusion, Helen was a primary author of the United States Environmental Protection Agency’s (USEPA’s) vapor intrusion guidance as well as several key USEPA technical documents and spreadsheet tools broadly used for evaluating the vapor intrusion pathway.
Todd is a Senior Consultant based in Ontario with more than 30 years of experience focused on contaminant fate and transport in soil and groundwater with a specialization in vapor intrusion and associated human health risks. Todd coauthored the first technical publication demonstrating the potential for enhanced groundwater contamination attributable to vapor diffusion. In 1997, he became the technical director of one of the world’s largest studies of subsurface vapor intrusion and has since conducted site-specific assessments of vapor intrusion at hundreds of sites throughout the world.
Established in 1995, ESTCP is the United States Department of Defense’s environmental technology demonstration and validation program. ESTCP promotes the transfer of innovative technologies that have successfully established proof of concept to field or production use.
More Information on the ESTCP Final Report on Vapor Intrusion
Read the report.
Learn more about ESTCP.
For more information on vapor intrusion assessments, contact Helen at hdawson@geosyntec.com or Todd at TMcAlary@Geosyntec.com.
Learn more about Helen: Helen Dawson
Learn more about Todd: Todd McAlary
