Roux Case Study: Undetected Vapor Intrusion Identified and Mitigated
Authored by: Ed Weagle, LSP, Nicole Hudson, CHMM, and Alfonso Sira
Roux recently assisted with the review of an industrial property in Massachusetts after state regulators issued a Notice of Noncompliance for an overdue environmental status report. Our work uncovered a previously undetected indoor air concern—highlighting how evolving guidance and new analytical tools can significantly change a site’s risk profile.
Why This Matters
Massachusetts state regulations currently require conservative methods for evaluating vapor intrusion—the movement of chemicals from soil or groundwater into indoor air—when compared to earlier approaches. Older vapor intrusion assessments may have relied on modeling approaches that are no longer accepted under current guidance. As a result, properties with older Response Action Outcomes (RAOs) or Temporary Solutions may unknowingly carry unresolved risks or compliance obligations.
Background & Results of Roux’s Updated Investigation
- Site Background: A previously filed Temporary Solution was supported by an out-of-date modeling-only vapor intrusion evaluation; current regulatory guidance requires the collection of environmental samples.
- Roux collected indoor air and sub-slab soil gas samples using procedures consistent with current Massachusetts vapor intrusion guidance.
- Results identified elevated concentrations of a chlorinated solvent (TCE) in indoor air and the subsurface.
- Levels exceeded the state’s threshold for an Imminent Hazard for sensitive populations.
Interim exposure reduction measures were implemented immediately, including enhanced ventilation and modifying building use. Roux partnered with a local vapor intrusion mitigation expert to design and rapidly install a sub-slab depressurization system (SSDS) to mitigate the vapor intrusion.
Roux’s SSDS effectiveness has been demonstrated through sub-slab pressure monitoring and follow-up indoor air sampling, which confirmed the effective mitigation of the TCE vapor intrusion. Regulators also required the termination of an Activity & Use Limitation (AUL) to reflect updated site conditions.
Key Takeaways for Property Owners/Operators, Lenders, & Attorneys
- Older environmental closures may no longer meet current standards. Sites with RAOs or Temporary Solutions filed before recent vapor intrusion guidance updates may be vulnerable.
- Periodic reviews are not optional. Regulators can issue violations when required periodic reviews or updates are missed.
- Updated assessment methods can reveal undetected risks—and help protect occupants.
- Proactive evaluation can prevent enforcement, project delays, and potential liability.
How Roux Can Help
Roux regularly assists clients with:
- Vapor intrusion evaluations and mitigation system design.
- Periodic review preparation and regulatory compliance.
- AUL review, modification, and termination.
- Indoor air quality assessments for commercial and industrial properties.
- Evaluation of existing mitigation systems.
- Second opinions on legacy environmental closures or prior consultant work.
If you’d like to discuss whether your sites may be affected by evolving vapor intrusion requirements—or if you’d like a second opinion on prior environmental work—our team is here to help. Please contact us directly below to get in touch with one of our experts.
