Vapor Intrusion Evaluations

Public and agency concerns regarding migration of volatile chemical vapors from  soils and shallow groundwater into residential, commercial and industrial buildings has prompted evaluation of vapor intrusion at newly identified contaminated sites, and in several cases, reevaluation of vapor intrusion and associated health risks for contaminated sites with cleanups long thought settled.  Vapor intrusion is the general term for the migration of hazardous chemical vapors from contaminated soil or groundwater through the subsurface environment and into nearby buildings.  Vapor Intrusion continues to be an emerging science, as investigation, data analysis, mitigation evaluation techniques and regulatory guidance continue to evolve. 

Exponent has conducted numerous vapor intrusion risk assessments including a range of evaluation of varying complexity at more than a dozen manufactured gas plant (MGP) sites in the Midwest, and an assessment for the MEW superfund site, one of the oldest superfund sites in California. Vapor intrusion is also a major issue in a number of litigations matters with claims of exposures and property damage from chemical vapors intruding into buildings associated with contaminated shallow groundwater and soils.

Vapor Intrusion

Vapor intrusion assessments often include collection of soil vapor and indoor air samples, data analysis, and use of a “multiple-lines of evidence” approach when evaluating potential residential and occupational health risks from the vapor intrusion pathway. Exponent has also assisted clients in proactively reviewing prospective vapor intrusion remedies and previously implemented remedies to ensure closed sites remain in compliance with recent 2015 EPA vapor intrusion guidance, with particular focus on perchloroethylene (PCE), trichloroethylene (TCE), and naphthalene in soils and groundwater.

Exponent Health Scientists, Industrial Hygienists, and Engineers provide comprehensive assistance to clients to address potential vapor intrusion issues including vapor-specific sampling in subsurface soils near buildings and beneath buildings, indoor air sampling, vapor intrusion modeling to estimate indoor concentrations of chemicals of potential concern, exposure assessments and risk assessments for occupants of effected buildings, and if necessary, development of vapor intrusion-based remediation targets.

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