Vapor intrusion can cause many serious problems. When contaminants enter indoor air systems, residents can suffer adverse health effects — ranging from headaches and nausea to increased cancer risks and organ failure. In addition to these health issues, vapor intrusion can also endanger the health and safety of a property. Flammable contaminants such as methane can increase the risk of fires or explosions. And sometimes contractors and developers can be liable for the negative effects of vapor intrusion.
Vapor intrusion mitigation systems (or VIMS) are designed to prevent vapor intrusion. There are two main types of VIMS — active and passive. Active vapor mitigation systems use mechanical means (i.e. as electric fans) to collect vapor from underneath a structure and expel it above the structure. A passive vapor mitigation system uses features such as vents and barriers, rather than mechanical solutions, to block and divert vapors from building up underneath the structure. Passive systems can be designed with room to be converted into active systems in the future if needed.
Why Are Passive Vapor Intrusion Barriers Used?
Passive mitigation is most commonly used in construction and redevelopment projects. Contaminated brownfield sites — or sites that have previously been developed but are no longer in use — are often subject to vapor intrusion. Passive vapor intrusion barriers are an effective way of mitigating this.
Passive vapor intrusion barriers are commonly composite barriers or single sheet membranes that are placed and secured to the building foundation elements. Prior to the installation of the passive barrier, a sub-slab venting collection system consisted of trenched PVC pipe or trenchless low-profile pipe is installed to collect and divert vapor to a series of vent risers. These vent risers then channel the vapor to above the roofline of the structure, where it can be safely expelled into the atmosphere.
Developers, other stakeholders and/or government regulations often require that VIM systems are implemented in construction and redevelopment projects.
What Are the General Requirements?
Different states have different requirements for vapor intrusion mitigation in projects. In some cases, there are no legal requirements, but recommendations and guidance are available for local state agencies. Organizations like the ITRC (Interstate Technology Regulatory Council) provide general guidance on how to properly mitigate vapor intrusion for new and existing structures.
ITRC vapor intrusion mitigation guidance and training are available on their site. If in doubt about the general requirements for a passive vapor mitigation system, a qualified environmental consultant can detail what kind of system your project requires and how it can be implemented.
How Are These Products Installed?
VIM systems are commonly installed underneath the foundations of buildings (known as the sub-slab area). For new construction, a passive barrier and vent collection system will be installed prior to the placement of concrete. If the structure is existing and portions of the existing slab are removed, then installing a passive barrier and venting might make sense. If concrete is not removed a topical coating can be applied to the existing concrete. The final alternative is to install an active system.
Installing a system during the construction of a new project is generally preferable. A passive mitigation system can vary in its components, but typically includes sub-slab vents and vapor intrusion membranes, which are available in a range of thicknesses. Whatever the specifics of your project, specialty contractors that are experienced in VIM can help plan and install the vents and barriers that make up a passive vapor mitigation system.
What Common Pitfalls Do General Contractors Experience?
Unfortunately, general contractors often experience missteps when it comes to planning and implementing truly effective VIM systems. Some common pitfalls include:
Failing to carefully read the environmental consultant's plans and requirements. This can cause important details to be missed. Even the smallest weak point in a VIM system can cause vapor intrusion.
Failing to adequately sequence construction to accommodate the mitigation system. This can lead to certain areas not being effectively protected by the passive vapor mitigation system.
No coordination with other trades involved in the project. Failing to communicate and plan how and when a VIM system will be installed can cause vital steps to be missed.
Changing the structure without fully notifying the environmental consultant. Environmental consultants have the expertise and experience to foresee how any changes will affect the efficiency of a VIM system. Bypassing their recommendations can lead to weaknesses in the structure.
What Are the Benefits of Passive Vapor Mitigation Systems?
These systems can mitigate vapor intrusion and the associated dangers (health issues, fire risks, etc.). Passive vapor mitigation systems can be installed where chemical vapors are already present or as a proactive measure.
Passive systems are significantly more cost-effective than active vapor mitigation systems and can be every bit as effective when installed optimally. They can also be customized to fit any type of structure.
How Can EPRO Help, and What System Might Work Best for You?
Our vapor intrusion barriers are made of impermeable composite materials that stop contaminant vapors from passing into structures. They are often used alongside vapor collection systems to alleviate the build-up of contaminated vapors within buildings. Our passive vapor mitigation systems are particularly suited to brownfield redevelopment sites and provide safety for future residents and neighbors of these sites.
Our VIM systems are comprised of one or more of these products, to suit individual requirements:
Geo-Seal 100: The most chemically-resistant composite vapor intrusion barrier on the market. It consists of three layers, including chemical-resistant HDPE sheets.
Geo-Seal EV80: A 79-millimeter-thick composite membrane that combines an Ethylene Vinyl Alcohol (EVOH), HDPE, and spray-applied polymer-modified asphalt.
Geo-Seal 60: The most cost-effective composite vapor intrusion barrier available. This product is particularly effective as a pre-emptive solution.
Geo-Seal EV40s: A single-sheet EVOH geocomposite vapor intrusion barrier, ideal for lower-risk sites, fast installations and use alongside active sub-slab ventilation systems.
Geo-Seal EFC: A chemically-resistant epoxy floor coating for existing structures. Applied to concrete floors, Geo-Seal EFC is formulated to mitigate chlorinated solvent and petroleum hydrocarbon vapors.
Vapor-Vent: A composite, low-profile vapor collection system designed to mitigate contaminated vapor and methane under overlying structures. Vapor-Vent can work as a passive vapor mitigation system or as a component of an active system.
Contact EPRO Today
We can help you choose the passive vapor mitigation to suit your project’s requirements.
Our process looks like this:
Our team will evaluate the site and goals of your project, and present you with product options to suit a range of budgets.
We will identify potential problems and challenges of your specific project, and provide creative solutions.
Additionally, we can provide technical support and advice as your products are installed to your specifications.