Sub-slab Depressurization System (SSDS).

The view above shows the initial layout of a network of four-inch diameter PVC pipes for a sub-slab depressurization system (SSDS) at an e-designated site in New York City. The pipe network is being laid beneath a proposed eight-story residential building. SSDS are recommended for sites with soil vapor issues. The SSDS is intended to mitigate soil vapors that could accumulate beneath a Site which could pose a significant risk to human health and the environment.

For this Site, an active SSDS was recommended due to elevated levels of perchloroethylene (PERC - Tetrachloroethylene) that was detected in post excavation soil vapor samples. The pipe network will be finished at the roof line with a 6-inch goose neck pipe to prevent rain infiltration. The pipes will be connected to a centrifugal blower which will create a negative pressure that will evacuate impacted soil vapor build up beneath the building foundation.