SECI has successfully installed and operated numerous Building Control Technology (BCT) or Sub – Slab Depressurization Systems  (SSDS) to address the Indoor Inhalation Exposure Route for Volatile Organic Compound contamination in former dry cleaning facilities and other manufacturing plants. The SSDS were constructed in accordance with the 35 IAC 742.1210 regulations.

The Sub-Slab Depressurization Systems typically consist of the installation of suction pits that provide overlapping coverage throughout the contaminated area.   The Sub–Slab Depressurization Systems are installed by saw cutting a two (2) foot square area into the concrete floor of a structure. The concrete is then removed, and the underlying soils are excavated to a depth of two (2) feet to allow for installation of the vapor recovery lines. The impacted soils excavated during the system installation are placed into 55 gallon drums and transported off – site for disposal under special waste manifests.  

After the soils are removed, the suction pits are backfilled with clean pea gravel to provide porous area for the soil vapor extraction line. The soil vapor lines consist of a three (3) inch in diameter, Schedule 80 - PVC piping that is slotted at two inch increments to allow for the collection and removal of soil vapors from beneath the concrete floor.

The soil vapor lines are connected to a solid riser pipe that is attached to the support columns/walls adjacent to each suction pit location. A “Home Aire RN 104 Radon Fan” is thenmounted to the columns, and the suction piping is attached to the fan.  Each suction pit is capable of creating a minimum radius of influence (at least -0.003 inches of water column) of 30 feet.

The discharge lines for the suction pits are plumbed to the exterior of the building. The exhaust lines are a minimum of ten (10) feet above grade and are not located near any operable windows or clean air intake vents on the building.

The intake line to the fans are fitted with pitot tubes to monitor the suction created at each pit location. The fans are then inspected on a daily basis by the building maintenance personnel to ensure that the system is working properly.  The systems are then continuously operated for the life of the building or until subsequent sampling is completed which verifies that soil vapor intrusion is no longer an exposure risk.