Demonstration/Validation of More Cost-Effective Methods for Mitigating Radon and VOC Subsurface Vapor Intrusion to Indoor Air

New lines of evidence and mathematical modeling are developed to aid in the design and performance monitoring of subslab venting systems for mitigation of radon and volatile organic compound vapor intrusion to protect the health of building occupants from inhalation exposures. The results indicate that the system performance depends strongly on the relative permeability of the floor slab and the material below the floor slab, and that both parameters can be determined with reasonable confidence using tests and analysis that are rapid and affordable. Where coarse granular fill is present below a high quality floor slab typical in DoD building stock, the radius of influence may extend to considerable distances, which reduces the number of suction points required and the associated capital cost. Where a system already exists, mass emission monitoring may help reduce the operation, maintenance and monitoring costs.