Ownership and redevelopment of brownfield properties can provide a business opportunity and greatly benefit a community. While there is significant potential for an all-around positive outcome, the owner or developer takes on the challenge of remediating or managing the contamination through working with environmental professionals and regulators. One of the most common challenges in managing contamination on these properties is dealing with vapor intrusion.
Vapor intrusion can occur when soil or groundwater underneath or adjacent to a building is impacted by “volatile” contaminants, meaning they readily exist as a vapor (i.e., gas). Think of the vapors that emanate from an open can of gasoline or other household chemicals such as paints and stains. When petroleum products or other volatile chemicals are spilled, they can seep into soil and groundwater and become an ongoing source of potentially harmful vapor. When these vapors move through soil and building foundations it can diminish indoor air quality. This is called vapor intrusion and can result in building occupants being exposed to these contaminants while breathing.
Vapor intrusion issues can be identified during due diligence, site development, or during characterization and remediation of known petroleum or other chemical spills. The nature and extent of the soil and groundwater contamination, as well as existing building conditions all have a significant impact on the best way to manage and resolve the vapor intrusion issue. It doesn’t matter if the building was constructed 200 years ago, 2 weeks ago or planned for construction in 2 months, there is a cost-effective solution. The solutions differ most significantly when considering mitigation of existing or new construction. Continue reading to learn more or call us at (610) 692-5770.
Vapor Intrusion Mitigation for an Existing Building
Vapor intrusion occurs when vapors migrate from beneath the building to indoor air through openings in the building foundation. These can be large openings such as a sump pit or dirt floor, or small openings such as cracks and small gaps in the concrete.
When vapor intrusion is identified as an issue, one of the simplest possible fixes is to seal cracks and gaps in the foundation that are readily allowing vapors to flow into the building. This can be done by installing special caps to sump pits, sealing cracks with specialized caulk, and sealing large openings with grout or concrete. Sometimes, just plugging up these holes is enough to limit the amount of vapors entering the building and resolve the issue.
Sealing the foundation might seem like the easiest path to pursue, but it is often not feasible or practical to seal an existing building foundation sufficiently to resolve the vapor intrusion issue. In this case, typically a sub-slab ventilation or sub-slab depressurization system is installed. The principle of both is to take the “contaminated” air from beneath the slab, transport it above the roof through pipes, and discharge it to the exterior above the breathing zone.
A passive system is a network of pipes connecting air beneath the slab to the exterior. The idea of the passive system is to provide a path of least resistance (i.e., the pipe) for the vapors to follow rather than migrating through the foundation and into the building.
An active system takes the idea of the passive system, but actively pulls vapors from beneath the slab through use of a fan. The fan creates negative pressure beneath the building foundation that prevents the contaminant vapors in the soil gas from migrating into the building.
Small Radial Type Fan for Active System 
Larger Blower for Active System
The current condition of the building foundation and permeability of the material beneath the slab have large influences on the best way to mitigate vapor intrusion for existing buildings. Brickhouse commonly conducts building inspections and initial diagnostic testing to assist developers and property owners in determining the most efficient and cost-effective manner to keep buildings in productive use while protecting the health of the building occupants.
Vapor Intrusion Mitigation for New Construction
Ask any developer and I’m sure they’ll agree that new construction is a complicated process. It takes a dedicated team of experienced professionals to take a new construction project from idea to reality. New construction at a brownfield property can add additional complexity to an already complex process. Fortunately, the best time to install a vapor mitigation system is during new construction.
Composite Vapor Barrier System Installed on Exterior Basement Walls 
Single Layer Vapor Barrier System Installed Prior to Pouring Basement Slab
As with any aspect of a construction project, proper planning with the right team and materials is paramount. Working with an environmental professional experienced in vapor mitigation system design and installation can help you to select the best approach and coordinate the installation with your design/construction team. Delays are going to happen in new construction and the addition of a vapor intrusion mitigation system installation will not add significant delays if properly planned and implemented.
Vapor intrusion mitigation systems and technologies are evolving rapidly, providing lower cost solutions and additional options to developers. The type of system selected will depend on the types of contaminants present, the severity of the contamination and the building construction specifics. While different systems exist, they all work using the same basic principles. During the construction of the building foundation, an engineered, chemically impermeable barrier (vapor barrier) is installed as a continuous envelope beneath the building slab. The vapor barrier may continue vertically up the foundation walls depending on the location of the soil or groundwater contamination in relation to the building foundation. The vapor barrier is placed above all sub-slab plumbing/conduits and sub-slab ventilation piping. The same sub-slab ventilation system this is installed to mitigate an existing building is also installed in new construction to provide a path for the vapors to escape above the roofline from below the vapor barrier. Similar to existing construction mitigation, these sub-slab ventilation systems can operate passively or as part of an active system using electric vacuum fans. It is important to realize that a vapor mitigation system that’s installed during new construction will tend to be more protective as a passive system than sub-slab ventilation systems that are installed in existing construction given that a chemically impermeable barrier is used in conjunction with sub-slab venting.
During and following the installation of these vapor mitigations systems, testing is conducted to ensure the continuity of the barrier and demonstrate that the system is effective in preventing the migration of harmful vapors into living spaces.
Next Steps
If you’ve read this far, we suspect you’re actively seeking solutions to a vapor intrusion issue or are as interested in healthy indoor air as we are. Contact us at dschott@brickhouse-environmental.com or shuxta@brickhouse-environmental.com to learn more about our vapor intrusion solutions.