Theme: 09. Vapor Intrusion

Topic Area: 9b. Vapor Intrusion Mitigation and Effectiveness

Formatted Title:

Successful Mitigation of VI Pathway through Innovative System Design

Background/Objectives:

As urban areas continue to expand into historically industrial neighborhoods where adaptive reuse is the predominant strategy for maximizing the value of built assets, exposure to industrial chemicals, including trichloroethylene (TCE), poses significant health risks. Vapor intrusion (VI) pathway mitigation for new buildings is a tried-and-true technology; however, VI mitigation in aging buildings requires creative solutions to work around programmatic constraints and keep occupants safe. A case study where an innovative VI solution was implemented to mitigate TCE exposure in an existing 100-year-old manufacturing warehouse that was converted into an entertainment venue in a trendy New York City neighborhood will be presented.

Approach/Activities:

TCE concentrations twice the immediate action level in indoor air and four orders of magnitude greater than the mitigation threshold in sub-slab vapor were first documented during due diligence, almost 10 years after conversion into an entertainment venue. When a communication test studying the efficacy of a traditional depressurization system yielded poor radius of influence (ROI) results due to subsurface obstructions, utilizing the sub-floor plenum between the finished floor and the foundation slab was evaluated as a potential solution. A VI mitigation system was uniquely designed to depressurize the sub-floor plenum—as opposed to depressurizing beneath the slab—resulting in a reduction from 28 suction points to only four, without penetrating the slab.

Results/Lessons Learned:

Two rounds of confirmation indoor air samples documented successful mitigation of the VI pathway, without downtime to the venue’s operations. Real-time remote monitoring provides assurance that the system is operating and minimizing exposure risk.

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Paul McMahon