The project involved the purchase of a large industrial machine shop facility that had been operating for over 65 years. Environmental work included the installation of 11 monitoring wells, including four deep nested wells to monitor the solvent impacts to groundwater. Vieau/GZA also completed two seasonal rounds of sub-slab vapor sampling within the building, collecting and analyzing more than 130 sub-slab vapor samples. The sub-slab vapor sampling defined distinct areas of concern within the building. Vieau/GZA designed and oversaw the installation of an active Sub-Slab Depressurization Vapor Mitigation System that provides adequate negative pressure throughout the areas of concern, protecting the building occupants from potential vapor intrusion. Vieau/GZA helped the buyer secure available environmental liability assurance letters from the Minnesota Pollution Control Agency (MPCA) and ultimately secure financing to purchase the property.


The large building footprint and heavy industrial operations at the site created a challenge to adequately define the areas of concern that require mitigation. The installation of a full-building vapor mitigation system would have been cost prohibitive (upwards of $750,000 or more).


Vieau/GZA organized the building into a 70-foot grid with the general goal to collect one sample within each grid quadrant. Sampling locations were reviewed and approved by the MPCA, and special attention was given to known areas of impacts and building additions to further aid in vapor mitigation decision making. Vieau/GZA sent out a team of six field professionals trained in sub-slab vapor sampling techniques to collect the required number of sub-slab vapor samples needed to properly evaluate the building per MPCA guidance. Sub-Slab vapor analysis detected five distinct areas of concern that required the installation of eight separate sub-slab vapor mitigation systems to provide adequate negative pressure to protect building occupants.


The buyer was able to secure financing, purchase the property, and remodel it for the existing use as a multi-tenant industrial building with over 30 tenants. The vapor mitigation system keeps the occupants safe from potential vapor intrusion and by installing the partial-building SSD System we saved the client upwards of $500,000.