Vapor Intrusion Mitigation Systems

Vapor-IntrusionVapor intrusion is the migration of volatile chemicals from subsurface soils or contaminated groundwater into overlying buildings. It has become a significant environmental issue for regulators, industry leaders, real estate developers, concerned residents, and other building occupants. Volatile organic compounds (VOCs) and methane (from nearby gas wells, landfills, or decomposition of buried vegetative matter) are typically the constituents of most concern. However, in some cases other chemicals may require consideration (e.g., certain semi-volatile organic compounds and some inorganic compounds, such as elemental mercury and hydrogen sulfide).

SCS Engineers provides a complete set of vapor intrusion mitigation services from evaluating the potential for vapor intrusion to designing, installing, and monitoring appropriate mitigation systems where necessary. Clients appreciate the single point of responsibility SCS provides as a “one-stop shop.”

It is not a simple matter to apply current regulatory guidance to determine the need for vapor intrusion mitigation. The actual intrusion (or expected intrusion in the case of new buildings) is often overstated, and some regulatory agencies use screening values for indoor air chemical concentrations that are at or below levels commonly found in buildings. The slightest error in sampling technique can dramatically affect the resulting data.

Where significant contamination is discovered beneath a building, the challenge is to design and install a system that is effective throughout the occupied space. Common approaches include retrofitting sub-slab depressurization systems, modifying the building ventilation system to overpressure the occupied space, and/or liners on top of floor slabs to reduce infiltration. For new building construction, passive venting systems and membrane barriers can be installed below new building floors. If necessary, the system can be made active by installing extraction blowers.

Whichever approach is taken, it is important to confirm the system is constructed properly and working as intended. Visual inspections, pressure measurements, and even smoke tests can be used to assure the quality of construction.

SCS offers the full array of vapor intrusion services for residential, commercial, and industrial properties, and for developers, municipalities, lenders, attorneys, industrial facilities, tenants, landlords, and buyers and sellers of real property.