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Vapor Intrusion Assessment and Remediation

As one of the preeminent firms for assessment and management of subsurface vapor intrusion to indoor air, our practitioners design innovative and cost-effective solutions to address our clients’ most challenging projects.

We specialize in providing services that include regulatory negotiation and litigation support, soil gas sampling, indoor air quality (IAQ) monitoring, mathematical modeling, customized mitigation system design and optimization, and ventilation assessment.

Our customized solutions add value and address risk by targeting corrective actions where they are warranted. Our practitioners are leaders in the field and are noted contributors to technical guidance documents published by regulatory agencies and industry associations.

Specialized Vapor Intrusion Experience

Regulatory Negotiation

Geosyntec practitioners have long-established credibility and expertise in the negotiation of regulatory approvals for our clients’ vapor intrusion needs. Our engineers and scientists participated in the development of more than a dozen regulatory guidance documents on vapor intrusion during the past two decades. This depth of knowledge and experience provides our clients with the ability to confidently negotiate sensible and cost-effective projects among local, state, and federal officials.

Litigation Support

Our legal clients include some of the world’s largest corporations and we have extensive experience in providing litigation support for cases where vapor intrusion or subsurface gas migration is a factor. These include cases related to human health impacts, medical monitoring, and property devaluation. We also specialize in the management of and access to large, complex databases for joint-defense groups.

Cutting-Edge Soil Gas Sampling

Through the use of our pioneering approaches, Geosyntec has conducted soil gas surveys in mobile gas chromatography, pneumatic testing, High Volume Purge sub-slab soil gas sampling, tracer testing, sampling in low permeability materials, and multi-phase partitioning assessments. Our practitioners developed sampling protocols for the Electric Power Research Institute (EPRI) and the United Kingdom Energy Institute as well as conducted extensive applied research and development of passive quantitative samplers for use in soil gas and 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 provided 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. Our long-term relationships with the world's leading laboratories and research institutes combined with 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 contributes to our reputation as leaders in the IAQ monitoring.

Mathematical Modeling

Geosyntec offers clients unprecedented expertise 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. 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 to indoor air.

Customized Mitigation System Design and Optimization

We provide engineering services for vapor intrusion mitigation system design, construction, operation, troubleshooting, and repair for both passive and active systems, including real-time control and monitoring services. As pioneers in the use of aerated flooring in the United States, we developed cost-effective methods to manage risk, particularly in new construction scenarios. Our patented sub-slab venting system is in use at brownfield sites found throughout the country and our current research explores the use of wind- and solar-powered systems for sub-slab ventilation.

Ventilation Assessment

Geosyntec practitioners apply heating, ventilating, and air-conditioning (HVAC) system manipulation to assess points of soil gas entry. This enables the establishment of 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 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 (EPA), the Electric Power Research Institute (EPRI), the Interstate Technology and Regulatory Council (ITRC), and ASTM International. The efforts associated with this public involvement represent significant steps forward in the evolution of vapor intrusion assessment and control technology.

In recent years, Geosyntec was retained by the U.S. Department of Defense (DoD) to compare four quantitative passive samplers to the conventional Summa canister method of sampling and analysis. We performed applied research with the University of Waterloo to develop another quantitative passive sampler, the Waterloo Membrane Sampler (WMS) ™, 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 and, like the WMS, have several advantages over conventional sampling, including simplicity of use, low cost, and small size, making them discrete, easy to ship, and useful in vent pipes.