Theme: 09. Vapor Intrusion

Topic Area: 9b. Vapor Intrusion Mitigation and Effectiveness

Formatted Title:

Mitigating Vapor Intrusion within an Active Manufacturing Building

Background/Objectives:

An environmental assessment of a small manufacturing facility located in Michigan found elevated concentrations of chlorinated volatile organic compounds (cVOCs), namely trichloroethylene (TCE), in groundwater and sub-slab soil vapor underlying the building footprint. The presumptive source was identified as historical operations of TCE degreasers as part of the facility’s manufacturing process. Concentrations of TCE in groundwater and soil vapor underlying the building exceeded applicable criteria established under Michigan’s environmental remediation regulatory framework for the vapor intrusion to indoor airspace and inhalation (VI) exposure pathway.

The client’s preferred path toward regulatory closure was to design and install engineering controls to actively mitigate intrusion of cVOCs to indoor airspace. Through pilot-scale testing, a sub-slab depressurization system (SSDS) was determined to be a viable and effective active mitigation strategy. Pilot testing also provided data to support the design and construction of the SSDS.

Approach/Activities:

Pilot testing was conducted at several locations in the facility to verify that the technology would be viable for the entire building. An evaluation of the pilot test results and sub-slab soil vapor sampling results was used to establish the configuration and design parameters for a full-scale system.

The detailed design process included an assessment of building conditions and extent of contamination to address VI concerns. Ultimately, the SSDS was designed so as to fully influence the entirety of the building footprint. The SSDS was installed during second shift to reduce the disruption of manufacturing operations. At the completion of construction, the efficacy of the SSDS was assessed and monitored following Michigan Department of Environment, Great Lakes, and Energy (EGLE) guidance. Data from each post-construction monitoring event were collected and evaluated to confirm SSDS efficacy and influence throughout the building.

Results/Lessons Learned:

Post-construction monitoring and collection of differential pressure readings throughout the manufacturing building confirmed the operation and efficacy of the SSDS. The installation of the SSDS was successful and is expected to contribute to the eventual regulatory closure of the on-site VI pathway. Collaboration with the client and other project stakeholders allowed the team to respond to concerns regarding the system operation and maintenance in a timely manner. Stakeholder collaboration was also helpful to accommodate the constraints associated with installing a mitigation system in a small, actively operating manufacturing facility. Due to spatial and operational constraints within the facility, adjustments to the original design needed to be conceptualized and implemented very promptly, without compromise of the design intent and functionality of the SSDS.

Menu

Allen Prince