Subsurface Vapor Intrusion Modeling and Assessments

Geosyntec Consultants maintains an international reputation as one of the preeminent firms for the assessment and management of subsurface vapor intrusion to indoor air. We earned our reputation by providing decades of innovation in applied research and practical project experience to the challenges presented by vapor intrusion at sites all over the world.

Clients seek us out for customized solutions founded in an understanding of physical, chemical, and biological processes. We design our solutions to add value and address risk by targeting corrective actions where they are warranted. Additionally, our professionals published the most widely cited and used vapor intrusion model (Johnson and Ettinger, 1991), and we have performed pioneering modeling of aerobic degradation of hydrocarbon vapors with the 3-D model of Abreau and Johnson (2005).

Geosyntec engineers and scientists are co-authors or contributing editors of guidance and regulatory documents that outline and advocate the latest advancements and research related to the remediation of vapor intrusion around the world. These include standards, information supplements, and handbooks issued by the U.S. Environmental Protection Agency, the Electric Power Research Institute, the Interstate Technology and Regulatory Council, and ASTM International, formerly known as the American Society for Testing and Materials. The efforts associated with this public involvement represent significant steps forward in the evolution of vapor intrusion assessment and control technology.

Our speciality areas include soil gas sampling, indoor air quality monitoring, mathematical modeling, and ventilation assessment.

Soil Gas Sampling

Geosyntec's soil gas surveys include the use of pioneering approaches in mobile gas chromatography, pneumatic testing, high volume purge sub-slab soil gas sampling (McAlary et al., 2010), tracer testing, sampling in low permeability materials (McAlary et al., 2009), and multi-phase partitioning assessments. Our practitioners developed sampling protocols for the Electric Power Research Institute (EPRI, 2005) and the United Kingdom Energy Institute (in press) and have conducted extensive applied research and development of passive quantitative samplers for use in soil gas, indoor, and outdoor air sampling.

Indoor Air Quality (IAQ) Monitoring

Our professionals have assessed indoor air quality as part of vapor intrusion investigations since 1992. We provide technical direction for one of the largest vapor intrusion investigations in the world, which required us to develop a new method of sampling and laboratory analysis to achieve reporting limits as low as three parts-per-trillion. We have established long-term relationships with the world's leading laboratories and research institutes and have extensive experience with both traditional and emerging methods for sampling volatile organic compounds (VOCs), semi-volatile compounds, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and other, less common compounds.

Mathematical Modeling

Geosyntec offers clients world-class experience in the application of vapor transport models. Our professionals co-developed the most widely used mathematical model for vapor intrusion to indoor air and use modeling to assist with targeted investigation design (Johnson and Ettinger, 1991) . We study large-scale, long-term vapor transport modeling and develop models with non-equilibrium phase partitioning for transient analysis of mass removal during soil vapor extraction. Our professionals established several forensic methods for discriminating indoor and outdoor sources of common VOCs from subsurface sources of VOCs to indoor air.

Ventilation Assessment

Geosyntec practitioners apply heating, ventilating, and air-conditioning (HVAC) system manipulation to assess points of soil gas entry. This allows us to establish target locations for sealants or other barriers, assess the sources of VOCs to indoor air, and implement means to mitigate the VI pathway. In some cases, minor modifications to an HVAC design or operations are sufficient to eliminate the vapor intrusion pathway while reducing or eliminating otherwise costly disruptions of manufacturing or retail operations.

Advancing the State of the Practice

Geosyntec continues to advance the state of the practice for subsurface vapor intrusion modeling and assessments through applied research and development. In recent years, the firm was retained by the U.S. Department of Defense to compare four quantitative passive samplers to the conventional Summa canister method of sampling and analysis.

Our practitioners also have performed applied research with the University of Waterloo to develop another quantitative passive sampler, the Waterloo Membrane Sampler™, and commercialize it for use in vapor intrusion assessments. Quantitative passive samplers provide long-term average concentrations, which are more relevant for assessing human health risks.

Image Link to Vapor Intrusion SoQ

More Information

For more information about Geosyntec’s comprehensive vapor intrusion and mitigation services, please see our Vapor Intrusion Statement of Qualifications »

Lead Consultants

  • Nancy Bice, P.G., CEG
    Nancy Bice is a Senior Principal Engineering Geologist based in California with more than 20 years of experience focused on the characterization and remediation of sites impacted by volatile organi ...
  • Karen Berry-Spark
    Karen Berry-Spark is a Senior Principal Hydrogeologist based in Ontario with more than 20 years of professional experience focused on the characterization and remediation of sites impacted by chlor ...
  • Helen Dawson, Ph.D.
    Helen Dawson is a Principal Civil and Environmental Engineer based in Washington, D.C. with more than 30 years of experience focused on private practice, academia, and public service. Her practice ...
  • Robert Ettinger
    Robert Ettinger is a Senior Principal Environmental Scientist based in California with more than 20 years of professional experience focused on the fate and transport of contaminants in the unsatur ...
  • Todd McAlary, Ph.D., P.Eng., P.G.
    Todd McAlary is a Senior Principal Engineer with more than 25 years of international consulting experience focused on the evaluation of contaminant fate and transport in soil and groundwater. ...
  • Peter Zeeb, Ph.D., P.G., LSP
    Peter Zeeb is a Senior Principal Hydrogeologist based in Massachusetts with more than 20 years of experience focused on investigation and remediation strategy at some of the most challenging sites ...
  • David Folkes, P.E.
    David Folkes is a Senior Principal Environmental Consultant based in Colorado with more than 35 years of experience focused on environmental and geotechnical consulting throughout the United States ...
  • Beau Hodge, P.G.
    Beau Hodge is a Principal Geologist based in North Carolina with more than 25 years of experience focused on environmental site investigation and remediation with a focus on recalcitrant compounds ...
  • Greg Corcoran, P.E.
    Greg Corcoran is a Senior Principal Civil Engineer based in California with more than 25 years of experience with a focus on the design, construction, and operation of engineered systems for waste ...
  • Sam Williams, P.G.
    Sam Williams is a Senior Principal Hydrogeologist based in California with more than 25 years of experience focused on the characterization and remediation of soil and groundwater contamination at ...
  • Duane Graves, Ph.D.
    Duane Graves is a Senior Principal Scientist based in Tennessee with more than 30 years of experience focused on environmental biotechnology; environmental forensics; in situ groundwater, soil, and ...
  • Mark Grivetti, P.G., CHG, CEG
    Mark Grivetti is a Senior Principal Hydrogeologist based in California with more than 30 years of experience focused on characterization and remediation of hazardous waste sites, surface and ground ...
  • Chris Herin, P.G.
    J. Chris Herin is a Senior Principal Hydrogeologist practitioner in the field of environmental risk management and minimization based in Florida with more than 25 years of experience focused on the ...
  • Susan Welt, M.P.H., P.E.
    Susan Welt is a Senior Engineer based in New York with almost 20 years of experience focused on the investigation and remediation of industrial sites, former manufactured gas plants (MGP), mining o ...
  • Tom Peel, Ph.D.
    Tom Peel is a Senior Principal based in Florida with more than 20 years of experience focused on environmental science and engineering including the development of regulatory and risk-based strateg ...
  • Mary deFlaun, Ph.D., BCES
    Mary deFlaun is a Senior Principal Environmental Scientist based in New Jersey with more than 20 years of experience focused on the development and implementation of in situ remediation technologie ...
  • Keith Tolson, Ph.D.
    Keith Tolson is a Senior Principal Environmental Scientist based in Florida with more than 15 years of experience focused on environmental sciences. He Specializes in the application of risk-based ...
  • Scott Drew, LSRP
    Scott Drew is a Principal Environmental Scientist based in New Jersey with more than 25 years of experience focused on the fields of environmental technology, site remediation, and environmental ch ...
  • Peter Dollar
    Peter Dollar is a Principal Hydrogeologist based in Ontario with more than 20 years of experience focused on site characterization, remediation strategy, remedial design and implementation, and ris ...
  • Todd Creamer, P.G.
    Todd Creamer is a Principal Geologist based in New England with more than 20 years of experience in environmental consulting services, surface water hydrology, and oil and natural gas exploration a ...
  • Robert Glazier, P.G.
    Robert Glazier is a Principal Environmental Consultant based in Maryland with more than 30 years of experience focused on site remediation, risk assessment, and environmental permitting associated ...
  • Daniel Schauer, P.G.
    Daniel Schauer is a Senior Principal Geologist based in Florida with over 24 years of geological, hydrogeological, and geotechnical engineering consulting experience focused on multidisciplinary en ...
  • Robert Veenstra
    Robert Veenstra is a Principal Environmental Engineer based in Missouri with more than 30 years of experience focused on developing and managing complex soil, groundwater and sediment investigation ...
  • Jeffrey Kurtz, Ph.D.
    Jeffrey Kurtz is a Senior Geologist based in Colorado with more than 30 years of experience focused on geochemical assessments, site investigations, and environmental forensics. Helping cli ...
  • James Cowart, P.E.
    James Cowart is a Senior Consultant based in Colorado with more than 35 years of experience focused on water quality permitting, industrial wastewater treatment, and watershed management throughout ...
  • Eric Tollefsrud, P.G.
    Eric Tollefsrud is a Principal Hydrogeologist based in Minneapolis with more than 25 years of environmental consulting experience focused on the characterization and remediation of soil, soil vapor ...
Geosyntec Consultants
Geosyntec is a specialized consulting and engineering firm that works with private and public sector clients to address new ventures and complex problems involving our environment, natural resources, and civil infrastructure.

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