by Wesley Robb — This article originally appeared in the May/June 2018 issue of FMJ
As more information is collected about the health effects of vapor intrusion, facility managers are beginning to take notice. Vapor intrusion is the potentially harmful migration of chemical vapors into a building from soil and groundwater that has been contaminated by volatile and semi-volatile organic compounds, and some inorganic analytes.
What is vapor intrusion?
Dry cleaning solvents and industrial degreasers are examples of volatile organic chemicals. Naphthalene is an example of semi-volatile organic chemicals, and radon would be an example of an inorganic chemical. The vapor intrusion of these chemicals cannot be detected by sight or smell, making it even more critical to be aware of the issue. Facility managers need to be confident that those working and occupying the building are breathing safe, clean air, and they need to do their best to avoid any kind of financial responsibility attached to any deviation of this.
By allowing individuals to work and occupy space where vapor intrusion may be occurring, those in charge of operating the facility could be opening themselves up to lawsuits. Class action lawsuits have been settled for up to US$8 million in the United States. In 2008, residents and business owners in the state of New York filed a lawsuit against IBM claiming US$100 million in damages. The town’s residents alleged the soil and groundwater were contaminated as a result of IBM’s former microelectronics plant. Microelectronics manufacturing facilities are known to have used chlorinated solvents such as Trichloroethylene (TCE) in their circuit board and microprocessor chip wafer production processes. IBM went on to install vapor mitigation systems in more than 300 homes. The case was ultimately settled, but no details were disclosed.
Risks from vapor intrusion
In a very similar way to how radon gas can affect a building’s inhabitable zone, so can vapor intrusion. In fact indoor air radon gas contamination is a specialized form of vapor intrusion, since the radon gas enters a building by the same mechanisms that a contaminated solvent or petroleum vapor would. The only difference is the radon gas is a natural consequence of the type of granite rock in bedrock below a building.
What is the difference between a vapor and a moisture barrier?
Vapor barriers are often confused with moisture barriers. They are two different types of products with two very different purposes.
Moisture barriers are designed to keep water in its liquid form from entering a building enclosure. It also keeps water from building up behind walls and under slabs to prevent the growth of mold.
Alternatively, a vapor barrier is part of a complete vapor mitigation system to prevent vapor intrusion. A vapor barrier blocks vapors from entering the breathing zone of a building.
Risk of vapor intrusion varies from one location to another due to their proximity to specific establishments which, currently or in the past, conducted operations that could have potentially contaminated the soil or groundwater. Other than Radon, the types of chemicals that are most associated with the phenomenon are volatile organic compounds, petroleum hydrocarbons and semi-volatile organic compounds. Hence, any existing development, or any development of property being considered near establishments that have used these chemicals should be assessed for the potential of vapor intrusion.
The EPA’s Hazard Ranking System and vapor intrusion
News and information regarding the effects of vapor intrusion continue to be released. These public statements and action taken by the Environmental Protection Agency (EPA) to mitigate the issue have served to heighten awareness of vapor intrusion as an issue to real estate transfer and development.
Recently, the EPA included vapor intrusion as a potential pathway in its Superfund Program. This has led to even more people in the industry learning about vapor intrusion and its potentially harmful effects. Furthermore, the EPA added a subsurface intrusion component to the Hazard Ranking System (HRS) on December 7, 2016.
The HRS is the principal mechanism the EPA uses to place sites on the National Priorities List. The addition of the subsurface intrusion component to the HRS meets the congressional mandate in Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) to identify releases of hazardous substances at sites that warrant further investigation. The EPA defines subsurface intrusion as the migration of hazardous substances and pollutants from the unsaturated zone and/or the surficial ground water into overlying structures.
The EPA states1 that Section 121 of CERCLA, as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA), requires that remedial actions which result in any hazardous substances, pollutants or contaminants remaining at the site be re-evaluated every five years to determine if the remedy is, and will continue to be, protective of human health and the environment.
OSWER Directive 9200.2-84 provides the recommended framework for assessing vapor intrusion in the context of the Superfund five-year review process – Assessing Protectiveness at Sites for Vapor Intrusion.
According to the EPA, Trichloroethylene is a widely used industrial chemical frequently found at Superfund sites as a contaminant in soil and groundwater. Furthermore, the EPA goes on to say that scientific evidence indicates Trichloroethylene poses potential cancer and non-cancer human health hazards. This has led to the EPA asking for more community and stakeholder involvement concerning the issue. As one example of a health hazard, the EPA has identified the risk of heart malformations to developing fetuses of women only seven weeks pregnant who have been exposed even to very low levels of TCE in indoor air.
What can facility managers do to mitigate vapor intrusion?
Consciousness of the issue is the first real barrier to overcome. By knowing that vapor intrusion is a potential concern for a facility, managers are able to take the necessary steps to mitigate the issue and do their best to avoid unnecessary future litigation. If the history of a facility’s site or surrounding areas make it a candidate for potential vapor intrusion, or if a manager is unsure of a site’s history and just wants to be safe, then the first step is to hire an environmental professional to conduct a Phase I Environmental Site Assessment and, if indicated, follow up with appropriate sampling and analysis.
When installing a vapor mitigation system before a structure is built, there are different options on the table. These are generally constructed in one of these three manners: a vapor barrier only installation, a passive or active sub-slab depressurization system (SSDS), similar to radon mitigation installation, or a combination system with a vapor barrier installed above an SSDS. These all allow the dangerous chemical vapors to be directed away from a building’s habitable zone.
The system chosen will depend on a number of factors such as specified construction requirements, type of chemical contaminants of concern and the prevalence of them in the soil, groundwater or soil vapor below the proposed building. An increasing number of construction projects are occurring on properties which necessitate the consideration of one of these types of vapor mitigation systems. But what if a building was constructed on a potentially dangerous site before vapor intrusion risks were on anyone’s mind?
Retrofitting a facility to mitigate the risk of vapor intrusion must be handled in a different way. If it’s determined by an assessment that vapor intrusion is a risk for a facility after it has already been constructed, options are limited. One of the most effective approaches is to apply a specially engineered sealant product to the basement floor and walls of the structure. This sealant is specifically designed to repel the sub-slab vapor that is trying to make its way into the structure. This approach has proven to be very effective, significantly reducing the amount of dangerous chemical vapors from intruding into the structure. Facility managers are leaning toward this option more often because the barrier itself doubles as a finished floor surface. Furthermore, it is an applied sealant, so there is no turning it “on” and “off.” It is always working.
If facility managers know vapor intrusion could be a potential issue for their facility, they should reach out to an environmental consulting company that is qualified to perform the necessary assessments, sampling and analysis, data interpretation and system design required to protect indoor air quality.
Wesley Robb is the director of technical strategies and applications of Vapor Mitigation Strategies and has more than 29 years of environmental field and laboratory experience, including several years of soil vapor sampling and analyses. Having joined Wellington Environmental Consulting and Construction in 2004, Wesley has managed on-site activities of various kinds: underground storage tank removals; soil remediation; Phase I investigations; vapor, soil, and groundwater sampling; and specialty sampling, including industrial hygiene sampling. To learn more, visit www.vapormitigationstrategies.com.