Vapor Barriers for Deep Foundation Supported Structures

Building construction on Brownfield sites, especially landfill sites, often requires the design and construction of vapor control systems for the purpose of minimizing the impact of subsurface vapors on building inhabitants. Vapor control systems are typically comprised of active or passive vapor extraction systems, a vapor barrier, and vapor monitoring systems and are integrated with the building foundation system. Integration of vapor control systems with deep foundation systems on settlement-prone subsoils and municipal solid waste (MSW) poses challenges not encountered on typical projects. Specifically, vapor control system elements require detailed design to account for potentially large amounts of settlement. Potential remedies typically involve structurally supporting vapor extraction piping, geomembrane vapor barriers, and subsurface vapor monitoring probes. However, structurally supporting vapor control system elements can be challenging and result in potential post-construction problems. Case histories are presented along with design considerations to avoid damage to the vapor extraction, monitoring, and barrier systems.