Vapor Intrusion Risk Assessment, Historical Manufacturing Site, Huntington Beach, California —
Tetra Tech conducted a human health risk assessment for potential vapor intrusion exposures to commercial workers for a site that was being reconfigured for commercial use by an internationally known clothing company. Historical manufacturing operations resulted in a release of VOCs to shallow groundwater. The evaluation was conducted using soil gas samples collected beneath the building and site-specific vapor intrusion modeling including actual building dimensions rather than the standard agency recommended default values to derive site-specific RBSLs for soil gas. The soil gas RBSLs were used to identify areas of the site posing an elevated vapor intrusion risk, which were mitigated by designing and installing a sub-slab venting system with mechanical ventilation. Tetra Tech worked closely with the client’s legal counsel and work was completed on an expedited schedule to meet the client’s schedule for remodeling the building.