Case Study: Managing PCBs in K-12 Schools via Encapsulation vs. Removal
by Matt Fragala, M.S., C.I.H. and David MacIntosh, Sc.D., C.I.H
The presence of elevated levels of PCBs (polychlorinated biphenyls) in K-12 schools has garnered nation-wide attention in recent years. Current estimates indicate that approximately 50% of public schools in the US were built during the time period (late 1950s to 1970s) when PCB-containing building products were commonly used. PCBs in building materials of schools pose a significant environmental liability to school districts and municipalities. The release of PCBs from building materials can sometimes lead to elevated concentrations in indoor air. Schools have struggled with how to address this issue because whole-sale removal and replacement of PCB-containing materials is extremely costly and disruptive and is therefore not a viable option for most schools.
This article presents a case study to illustrate how a remediation plan that incorporates techniques to contain PCBs can effectively reduce indoor air concentrations while controlling costs and minimizing disruption.
Managing PCBs in an Elementary School
Elevated levels of PCBs were discovered in a New England elementary school as part of a proactive property management program. Subsequent building characterization identified PCBs in indoor air of the school as a concern for health risk. The school system and town were faced with managing the regulatory and environmental health aspects of PCBs while maintaining an effective and safe environment for learning and working. EH&E undertook a multi-faceted effort to guide the school system and community through this process. Principal components of the response included identification of PCB sources in the school; design of mitigation methods; oversight of abatement and HVAC contractors; communication of risks and project status to educators and the community; facilitation of interactions with the EPA (US Environmental Protection Agency) and the State; and development of the Operations and Maintenance Plan.
As the first step, a complete characterization of the building was conducted to identify PCB-containing building materials. The characterization included the building exterior and interior and focused on different types of caulking and sealants as well as fluorescent light ballasts. Based on the results of the building characterization, primary and secondary sources of PCBs were identified and prioritized based on their potential to contribute to occupant exposure.
A site specific risk assessment of the school was performed next. Public health guidelines have been established by the EPA; however, these guidelines are based on generic assumptions for key criteria such as occupancy. The benefit of the site specific risk assessment is that the analysis is based on the unique use of the school to provide a better assessment of the site risks. Results of the risk assessment established targets for acceptable levels of PCBs in indoor air of the school and provided a benchmark against which to evaluate alternative mitigation methods.
Mitigation methods were implemented in a staged approach to minimize disruption of school operations and to manage costs. Primary sources of PCBs identified by the building characterization were addressed first and follow-up testing was conducted to measure progress. This process of implementing mitigation strategies and follow-up testing was conducted until the target PCB levels, identified by the site specific risk assessment, were achieved. The step-wise process allowed the school to re-occupy areas as they were determined to meet the established criteria based on the air and surface sampling results; thereby helping to minimize disruption to school activities and control cost.
All the results of the sampling and remediation were made available to the community via public meeting and the school system’s website. Parents and teachers were able to see that progress was being made with each phase of remediation and this helped to alleviate concerns and build trust. EH&E worked closely with the superintendent’s advisory committee and participated in public meetings to keep the community informed of the potential risks, the remediation plan and its progress. In addition, valuable information was provided to EH&E in these meetings that assisted in decreasing potential risks and minimizing disruption for the students.
PCB levels were successfully reduced to the target levels throughout the school. Remediation included removal of some PCB caulking but largely focused on isolating PCB-containing materials from the indoor environment, cleaning surfaces, and modifying the HVAC (heating, ventilation, and air conditioning) system to optimize ventilation with outdoor air. Isolation and cleaning involves minimizing transfer of PCBs from source materials to indoor air and surfaces inhaled or contacted by building occupants. Ventilation involves displacing indoor air that may contain PCBs leaked from source materials with clean outdoor air. More information on the various mitigation methods are described below.
Window Sealants and Glazing Compounds
Window sealants and glazing compounds on the interior and exterior of the windows were identified as primary sources of PCBs. These materials were encapsulated using a two-part system comprised of Bond Breaker tape and silicone caulk. This system provided an effective barrier and has the adhering qualities needed to stand up to weathering.
Brick and Metal Window Frames
The porous brick material surrounding windows was encapsulated with a two-part epoxy compound and the non-porous metal window frame was cleaned to post-abatement clearance criteria.
The release of PCBs from the curtain walls (window assemblies) was identified as a significant contributor to PCB levels in indoor air. A two-part system consisting of encapsulation and physical barriers was used to limit emissions of PCB vapors into classrooms. After encapsulating the PCB caulk with silicone caulk and Bond Breaker tape, a gypsum board wall was constructed over the portions of the curtain wall that contained PCB caulk, thereby separating those source materials from indoor air. (See Figure 1.)
Modifications to the HVAC were made in collaboration with the school facilities staff and HVAC contractors. The intent of these changes was to maximize the delivery of outdoor air into the school. These modifications proved to be successful in helping to minimize airborne PCB levels in the school and improve overall indoor environmental quality.
As a follow-up to remediation, EH&E developed an Operations and Maintenance (O&M) Plan for the school to ensure the continued mitigation of potential risks associated with PCBs in building materials. The O&M Plan includes specifications for continued sampling and measurements to verify the continued efficacy of encapsulation and ventilation with outdoor air. Awareness training for workers and teachers is another important component of the O&M Plan.
As a result of the remediation efforts and ongoing maintenance program, the elementary school meets all of the indoor environmental quality requirements for faculty and students and is fully functioning. The encapsulation techniques and HVAC modifications proved successful in mitigating PCBs risks and were significantly less costly and less disruptive than complete removal and replacement.
Matt Fragala is Practice Director, Education and Commercial, at EH&E and has served as a project manager and field team member for over 100 indoor environmental quality investigations involving various indoor air quality parameters, such as volatile organic compounds, PCBs, particulates, bacteria, and fungi. For more information contact Matt at MFragala@eheinc.com.
David MacIntosh is Director of Advanced Analytics at EH&E. David leads exposure, health impact, and life cycle analyses for commercial, government, and non-profit organizations. For more information, contact David at DMacIntosh@eheinc.com.