Vapor intrusion occurs when volatile organic compounds in soil and groundwater enter buildings as vapors and create health and safety risks for the occupants. Vapor intrusion can occur at any property, including active and shuttered factories, gas stations, strip-mall dry cleaners, and others. Vapors can also encroach on neighboring sites, such as residential and commercial properties, resulting in unsafe conditions.
BBJ Group has supported clients globally in identifying, quantifying, and mitigating vapor intrusion risks.
Vapor intrusion creates risks that affect the safety, value, use, and marketability of affected properties. New, overlapping, and sometimes contradictory vapor intrusion regulations catalyze these concerns by increasing awareness – and disagreement – regarding the risk. Adding to the concern is the possibility of personal injury claims from tenants or third parties alleging vapor exposure.
Mitigating vapor intrusion is most easily done as part of new building construction. As such, for new developments, BBJ partners with the client to seamlessly incorporate mitigation solutions into the project design. However pre-existing buildings can also be retrofit with vapor intrusion mitigation systems, such as a sub-slab depressurization system.
The potential for vapor intrusion is typically first assessed by conducting a vapor encroachment screening that meets the ASTM E2600-15 standard. Such screening often occurs as part of a Phase I Environmental Site Assessment due diligence prior to a real estate transaction.
Where necessary, based on the results of vapor encroachment screening, BBJ Group can investigate the potential for vapor intrusion by evaluating sample data collected on-site. An evaluation may consist of collecting soil gas or groundwater samples, or modeling existing data from prior investigations.
When sub-slab soil gas sampling or other intrusive investigation is impractical, BBJ Group uses non-intrusive flux chamber surveys to understand the subsurface conditions that may be affecting indoor air. This approach allows an evaluation of vapor intrusion potential while eliminating interference from ambient background sources. In addition, flux chamber investigations can be conducted without breaking ground, making this a convenient solution for leased spaces.
Properties that have a history of solvent or petroleum usage have the potential to have a vapor intrusion condition. Common operations include, but are not limited to:
Where remediation is impractical, mitigating vapor intrusion impacts within a building can be a useful approach to minimize exposure. Such technologies include:
During acquisition due diligence of a manufacturing facility in the Chesapeake Bay watershed, BBJ Group identified free phase at an adjacent site. BBJ Group performed a soil DNAPLS gas survey and indoor air investigation, identifying potentially harmful levels of TCE vapors affecting the building. BBJ Group designed and installed a sub-slab depressurization system, reducing TCE concentrations to EPA-approved levels.
BBJ Group provides vapor intrusion assessment services for multiple national commercial clients. One company is a telecom retailer with leases across the U.S. BBJ Group has developed methodologies to evaluate vapor risks and support successful lease negotiations, making landlords aware of vapor issues while offering practical solutions that address our clients’ H&S and risk mitigation requirements.
Kevin McCartney, P.G.