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 »

Our 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 organic compounds. She specializes in innovative site characterization techniques, and the design and implementation of groundwater remediation systems. Nancy has developed site-specific soil and groundwater remediation applications for some of the most complex sites in California regulated under Californ ...
  • 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 chlorinated solvents and other dense non-aqueous phase liquids (DNAPLs) in soil and groundwater. Karen has developed site-specific remedies using in situ bioremediation, zero-valent iron, and related technologies at sites throughout North America. Karen's practice also focuses on the assessment a ...
  • 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 spans a wide range of technical disciplines including vapor intrusion, groundwater characterization, and contaminant fate and transport modeling related to the spread of dense non-aqueous phase liquids, chlorinated solvents, and metals in the environment. Sought out for regulatory analysis a ...
  • 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. Todd specializes in assessing and mitigating the migration of volatile organic compound (VOC) vapor from the sub-surface environment into buildings and in the assessment of human health risks associated with inhalation exposure. He co-authored the first technical publication demonstrating the pot ...
  • 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 unsaturated zone, including soil vapor extraction system design, vapor emission estimation, and subsurface contaminant vapor migration to indoor air. Robbie has extensive experience in assessing potential subsurface vapor intrusion to indoor air associated with former and current gasoline retail an ...
  • 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 in the country, including CERCLA-regulated sites in New England and the Midwest, as well as numerous state-regulated sites. Specializing in site investigations, modeling, pilot tests, remedial strategy development/alternatives analyses, and full-scale remedy design for more than 20 years, Pe ...
  • 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 and Canada. One of the nation's foremost experts on vapor intrusion (VI) evaluation and mitigation, Dave was invited by U.S. EPA to address the national Resource Conservation and Recovery Act meetings held in 2000 and 2002 on VI issues impacting sites throughout the country. Dave also was a ...
  • 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 including chlorinated solvents, creosote, and coal tars. He is a professional geologist with expertise in developing assessment, remediation, and closure strategies. Beau is a Registered Site Manager under the North Carolina Registered Environmental Consultant Program, the voluntary remediat ...
  • 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 containment facilities and brownfield sites impacted by contaminants in soil, soil gas, and groundwater.  During his career, he has become a recognized national expert in the design, permitting, and construction of liner and cover systems for municipal, industrial, mine, mill, and haza ...
  • 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 industrial and commercial properties. Utilizing his experience in site characterization and innovative remediation programs to work with clients on converting impacted properties into community assets as commercial developments through Brownfields site redevelopment programs, Sam has worked ...
  • 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 sediment remediation; evaluation of airborne biological contaminants; and remediation of groundwater in karst formations. Duane specializes in the development, selection, feasibility evaluation, design, and deployment of remedial solutions for hazardous, radioactive, and mixed-waste, contam ...
  • 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 operations, and U.S. Department of Defense facilities.  She is an experienced strategic planner and risk communicator and manager of soil, groundwater, sediment, and vapor intrusion (VI) projects. Susan's practice also focuses on the risk-based management of contaminated sediments and th ...
  • 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 groundwater resource management, and engineering geology studies for a wide range of projects. He brings creative environmental solutions to the redevelopment of complex sites impacted by soil and groundwater contamination. Mark's worldwide experience in the investigation and remediation of comple ...
  • 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 mitigation of environmentally impaired properties, environmental compliance, due diligence (All Appropriate Inquiry), and cost-to-cure estimates. He also specializes in groundwater studies, contaminant fate and transport evaluations, and waste management. He is often tapped to serve as a technical ...
  • Keith Tolson, Ph.D.

    Keith Tolson is a Senior Principal Environmental Scientist with more than 15 years of experience focused on environmental sciences. He Specializes in the application of risk-based principles to support legal and regulatory requirements. Keith provides expert technical and strategic consultation on matters related to regulatory compliance and litigation. He also develops and supports public risk communication concerning the health effects of chemicals in air, water, soil, sediments, consumer p ...
  • 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 strategies to obtain cost effective closure and redevelopment for environmentally impacted properties. He specializes in applying innovative risk-based approaches to reduce the cost of site assessment and remediation activities. Tom has directed investigations and remedial strategy development for ...
  • 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 chemistry. His practice focuses on the in situ remediation of organic compounds, including chlorinated solvents, explosives, and MTBE. His recent work in fractured rock environments has included the application of anaerobic bioaugmentation in mudstones and biosparging in karst. Over the course ...
  • 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 technologies. Mary has practical experience bringing in situ remediation technologies addressing recalcitrant organics and metals from bench and pilot scale applications to practical field applications. She has applied technologies such as biostimulation and bioaugmentation to impacted soil and groundw ...
  • 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 risk management. In particular, his professional practice focuses on the characterization and remediation of sites impacted by chlorinated solvents, petroleum hydrocarbons, and metals in soil and groundwater. His technical expertise is focused on the geochemistry of contaminated soils and groun ...
  • 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 and production. His work has focused on the characterization of and remedial strategy for industrial, institutional and residential properties impacted by chlorinated solvents and petroleum hydrocarbons. Specializing in vapor intrusion of volatile compounds into indoor air and LNAPL behavior ...
  • 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 with solid and hazardous waste landfills as well as power generation and manufacturing facilities. Bob's consulting services focus on the strategic management of environmental liabilities, working with private sector clients who want to reduce financial exposures associated with cleaning up ...
  • 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 engineering contracts for federal, municipal, and private clients throughout the U.S. and abroad. His practice focuses on construction management, construction engineering, landfill reclamation, construction QA/QC, and remedial system O&M. To assist his clients, Dan has used his geologic a ...
  • 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 clients to protect human health, Jeff complies with regulatory requirements, minimizes potential third party liabilities, and helps to remediate complex sites impacted by vapors from contaminated soil and groundwater. He also specializes in geochemical field investigations and assessments of the fate a ...
  • 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 and remediation programs associated with large petroleum facilities (refineries, terminals, tank farms, E&P properties, etc.) and chemical manufacturing facilities and former manufactured gas plants under the requirements of RCRA Corrective Action, CERCLA, and numerous state-lead programs. ...
  • 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 the United States. He also conducts numerous vapor intrusion investigations and directs large-scale voluntary cleanups for mines, manufacturing plants, and brownfield redevelopment sites, among others. Assisting clients in numerous industries, Jim has worked closely with oil and gas product ...
  • 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, and groundwater contamination at industrial and commercial properties. With expertise in complex site characterization and environmental remediation projects, Eric uses state-of-the-practice technologies to help clients make better informed decisions regarding the remediation of contaminat ...
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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