Vapor Intrusion Mitigation System for Brownfield Redevelopment

MAE2 was selected to help design an active Sub Slab Depressurization system for a new construction site that had high levels of TCE and PCE in the soils.

The project goal was to redevelop a former factory building creating new retail, restaurant, and office space. A solution needed to be developed to keep any contaminated vapors in the soils from releasing into the occupied building spaces. Space was a premium, so the system needed to protect the building occupants with as small a footprint as possible.

MAE2 worked with the consultant prior to the building construction to design an active vacuum blower system that had enough capacity to remove any vapors from the sub slab. Three outdoor weather skids that would be placed upon the building roof were selected so that no valuable floor space would be lost.

The skids were designed with trouble free, simple weather proof controls to maximize system up time. A series of slotted pipes were placed underneath the building slab and connected to a main trunk line that extended to the roof and connected to the blowers. The design goal was to prevent any hazardous vapors that reached the sub slab foundation from intruding into the occupied areas above. There were two smaller areas in one building section and a larger area in a second section. The smaller zones were connected to 10 HP pressure blowers and the larger zone was connected to a 20 HP blower. The blowers were designed for vacuum applications and are able to move large volumes of air at 20” WC.

The start up of the sub slab depressurization skids was very successful and the high volume air exchange had significant influence and prevented measurable volumes of TCE, PCE vapors from entering the finished spaces.