Phase I – Environmental Site Assessments

Vapor Intrusion Studies

Vapor intrusion (VI) is the migration of volatile organic compounds (VOCs) from an underground source through soil or other pathways into buildings. Volatile chemicals in buried wastes and/or contaminated groundwater can emit vapors that may migrate through subsurface soils and into indoor air spaces of overlying buildings. A Vapor Intrusion Survey is required when impacts to the subsurface have been identified. The survey provides information on general building characteristics, points where soil gas may enter the building, and potential indoor contaminant sources.

Vapor Intrusion Surveys are conducted through a Tier I and/or Tier II VI Screening approach conducted in accordance with the Environmental Protection Agency (EPA) guidance. A Tier I VI Screening consists of an analysis of potential contaminants of concern sources (on-site or off-site) and pathways into the building(s). A Tier II Vapor Intrusion Screening consists of sub-slab vapor sample and indoor ambient air sample collection and laboratory analysis to determine if vapors of concern are present within the building(s).

What is a Vapor Intrusion Survey?

A Vapor Intrusion Survey is an investigation into the potential for harmful chemical vapors to enter buildings and other enclosed spaces from contaminated soil or groundwater. It typically involves a detailed evaluation of the site’s history, the nature and extent of the contamination, and the potential pathways by which vapors could migrate into indoor spaces.

During a Vapor Intrusion Survey, environmental professionals may collect samples of soil, groundwater, and indoor air to assess the concentration of volatile organic compounds (VOCs) and other chemicals that can evaporate and become airborne. They may also conduct air pressure tests and measurements of the building’s ventilation system to determine the potential for vapor intrusion.

The findings of a Vapor Intrusion Survey can be used to develop a remediation plan to mitigate the risks posed by vapor intrusion. This may include the installation of vapor barriers or ventilation systems to prevent the entry of vapors into the building, or the removal and treatment of the contaminated soil or groundwater to reduce the potential for vapor intrusion in the future.

Vapor Intrusion Studies are typically conducted in conjunction with environmental site assessments and other investigations to assess the overall environmental risks posed by contaminated sites.

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