March 11

Apartment Complex Mitigates Vapor Intrusion

A Wisconsin Apartment Complex was located on the former Appleton Wire Works site, a manufacturing facility that began operation in the late 1800s. The site had been partially remediated before the issuance of regulatory guidance on investigating vapor intrusion beneath and inside buildings. After vapor intrusion became a regulatory focus, the Wisconsin Department of Natural Resources (WDNR) directed an initial vapor intrusion assessment, including collecting and analyzing sub-slab vapor, including vapor from beneath the floor of the buildings and indoor air samples. The results of this assessment revealed trichloroethene (TCE) in both indoor air and sub-slab vapor at concentrations above regulatory thresholds. As a result, EnviroForensics was contracted to conduct additional vapor intrusion assessment and mitigation activities. 


EnviroForensics conducted additional vapor intrusion sampling and sub-slab pressure testing for purposes of mitigation design. Designed a sub-slab depressurization system (SSDS) consisting of 10 individual fans to mitigate vapors in all occupied spaces of the apartment complex. Assembled informational materials and held an open house for all stakeholders, including residents, media, regulators, and concerned citizens, in advance of the SSDS installation. Mitigated the apartment complex complicated with multiple layer flooring system, in-floor radiant heating lines, and a Combination of flat and pitched rooftops. Conducted post-installation pressure confirmation testing and several indoor air sampling events. Installed a remote alarm system that provides notification in the event of pressure loss. 


The SSDS achieved the required sub-slab pressure differentials, and the post-installation indoor air sampling results confirmed successful mitigation in all areas. Operation and maintenance of the SSDS continue while additional groundwater remediation is ongoing.