School Construction News recently connected with Jackie Robb, principal, Vapor Mitigation Strategies, for a Q&A on smart approaches to vapor mitigation at school facilities — and why the effort can be so crucial for today’s educational venues.
Q: Why is vapor mitigation so important, particularly for educational facilities?
Robb: Vapor intrusion (VI) is a concern as contaminants in the breathing space of a building can seriously compromise the health of the building occupants.
Maintaining safe schools for all building occupants is of paramount importance for school administrators. While vapor mitigation is important in all structures with known or potential vapor intrusion, it is particularly important in educational facilities as children and some staff (the elderly, pregnant, and health compromised) are sensitive receptors. As sensitive receptors, children and some staff may be more adversely impacted by contaminants due to their age (children and the elderly) and health issues (illnesses, medications, pregnancy, overall health).
It is important to remember that kids and staff likely spend more time in school buildings than any other structure beside their home.
Q: What situations would prompt a school administrator to question if they may have a vapor intrusion situation?
Robb: If the school property or surrounding properties are currently or were historically used by any of the following, a potential for vapor intrusion may exist:
- Gasoline station
- Automobile repair shop
- Dry cleaner
- Printing company
- Manufacturing facility
Q: Can you tell me in a nutshell about passive systems versus active systems?
Robb: The main difference between passive and active systems is that a passive system has no mechanical pump or fan to move the soil vapor below the building. A passive system relies solely on a barrier and/or vent channels to allow the toxic gasses below the structure to migrate away from the sub-slab so that they will not enter the breathing zone of the building.
An active system utilizes a mechanically driven pump or fan to force the soil vapor through channels below the sub-slab and away from the building. With this type of system, an Operations and Maintenance (O&M) plan involving routine inspection of the mechanics is required to ensure it is performing its task to reduce vapor intrusion into the structure above. In some circumstances, a combination is installed which includes active sub-slab venting to force soil gas away from the sub-slab and a vapor mitigation barrier to reduce slow absorption and penetration through the sub-slab.
Both can be effective vapor mitigation strategies to potential vapor intrusion. The choice would depend on factors unique to each building or campus. Factors in the design process include the following: size of building(s), type of contaminants, concentration of toxic chemicals in the soil vapor, proximity of groundwater to the sub-slab, underground utilities and penetrations, and budget, to name a few.
Q: Is one system more effective than the other? More affordable?
Robb: There are a myriad of factors that impact the effectiveness and the cost of each system. In broad general terms, passive systems are less costly because they have fewer upfront costs (motor, power supply, etc.) as well as ongoing costs (electricity, maintenance, equipment replacement). Active systems are more effective as they are actively removing contaminated vapor from beneath the sub-slab, however, they are dependent on electricity for continued operation. Therefore, a power outage will stop the active removal of contaminants. A vapor barrier can be used in conjunction with either system.
It is important to remember that active systems are not necessary in all situations. The individual nature of each facility and associated contamination should be studied in order to be sure the system chosen adequately addresses the need without over design, which could result in unnecessary costs.
Q: Are there any big trends in school’s using vapor mitigation? Do you have any idea what percentage of American public schools currently employ some kind of vapor mitigation?
Robb: As vapor intrusion is still a relatively new environmental concern, vapor mitigation is still in its infancy. That being said, dozens, perhaps hundreds of schools, have had vapor mitigation systems of some type installed.
Although vapor intrusion may be a concern in any number of existing school buildings and new construction of school facilities, we see the largest emerging potential for vapor mitigation in schools moving into non-traditional school spaces. More and more, Charter Schools are looking to non-traditional buildings such as former commercial, warehouse, and industrial spaces in an effort to save costs and find space in highly urbanized areas. It is important that administrators looking at new locations are aware of types of businesses which were historically located on and/or around the property. Retail spaces may include former dry cleaners and gasoline service stations. Warehouse and manufacturing facilities could have used or stored a broad range of industrial chemicals and solvents.
Q:What would you tell a school administrator who was considering a vapor mitigation system for the first time?
Robb: As one can see, there are multiple items for consideration with respect to vapor intrusion and corresponding vapor mitigation strategies to utilize. The school administrator should retain the services of an environmental professional who can develop a site-specific mitigation plan and assist them with implementation and maintenance.
Jackie Robb, CHMM, serves as the principal of Vapor Mitigation Strategies. Jackie has more than 25 years of environmental engineering and consulting experience conducting Phase I Environmental Site Assessments including Vapor Encroachment Screens (VECs) and Phase II Subsurface Investigations including soil vapor sampling, as well as underground storage tank closures and soil remediation.