Managing the threat of vapor intrusion has become an all too familiar challenge for many brownfield redevelopers and commercial property owners. Vapor intrusion occurs when vapors migrate from contaminated soil or groundwater into an overlying or adjacent building. The risk, or challenge, arises when people breathe these vapors and potentially experience negative health effects. Brickhouse assists clients through these challenges, from the initial phase of determining the risk of vapor intrusion to developing the most cost-effective and least disruptive solutions when mitigation is necessary.
How do I know if vapor intrusion is a concern for my existing or proposed building?
For vapor intrusion to be an issue, there needs to be a source of the vapor. Vapor can come from soil or groundwater impacted by Compounds of Potential Indoor Air Concern (COPIACs) near the building. The PADEP has defined “near” as within 30 to 100 feet of the building, depending on what type of contaminants are present.
One of the most common ways the presence or likely presence of this soil or groundwater impact is identified is through the staged process of environmental due diligence, starting with a Phase I Environmental Site Assessment and moving to a Phase II Environmental Site Assessment, if warranted. If during the due diligence process the presence of soil or groundwater impacted by COPIACs can be ruled out, then no further consideration of vapor intrusion is necessary.
What happens next if I have soil or groundwater impact near my building?
Finding a source of vapors does not necessarily mean a burly mitigation system is needed. State and federal agencies have published extensive guidance on steps to further evaluate risk to surrounding buildings. Depending on the current state of the property and the nature of the soil or groundwater impact, the evaluation may be as simple as comparing data to published screening values. Alternatively, it may require sampling of 1) the air between the soil particles within the area of impact, 2) the air beneath the slab of the building, or 3) air within the building. Brickhouse has extensive experience designing these sampling programs and utilizing the data to determine if mitigation measures are warranted.
It looks like I need to manage a vapor intrusion issue. What now?
The most common options for mitigating vapor intrusion are vapor barriers, sub-slab ventilation or depressurization systems, or a combination thereof. Vapor barriers are typically installed beneath the building pad and are commonly used in new construction. These barriers come in various thicknesses and can be installed through several different methods. Brickhouse commonly consults with the development team to determine the best vapor barrier for a new building.
Sub-slab ventilation or depressurization systems are installed in both existing buildings and new construction. A ventilation system provides a pathway (pipe) for vapors from beneath the slab to passively vent to ambient air. A sub-slab depressurization system includes a fan that actively removes air from beneath the building slab and discharges it to ambient air. These systems are often installed as passive systems with the capability to convert to an active system, if necessary.
Vapor intrusion is a part of Brickhouse Environmental’s scientists and engineers daily work, from the initial due diligence phase through the design and installation of mitigation systems. We look forward to working with you to implement cost-effective, working solutions that serve your project goals.