Vapor Intrusion to Indoor Air Assessment and Mitigation representative project experience includes:
Indoor Air Evaluation for Semiconductor Manufacturer
Development and implementation of an indoor air evaluation for a semiconductor manufacturer in Santa Clara. The site has residual concentrations of volatile organic compounds in subsurface soil and shallow groundwater. At the request of the San Francisco Bay Regional Water Quality Control Board, an evaluation of potential vapor intrusion of the volatile organic compounds from the subsurface to indoor air was evaluated by collecting a combination of soil gas samples, indoor air samples, and ambient air samples. The data was used to estimate potential indoor air excess cancer risks and noncancer hazards. The results of the evaluation indicated that volatile organic compounds were present in soil gas, but there was no evidence of indoor air vapor intrusion. Indoor air concentrations were found to be similar to ambient outdoor air concentrations and estimates of excess cancer risks and noncancer hazards were less than acceptable levels.
Indoor Air Evaluation for Daycare Center
Development and implementation of an indoor air investigation and evaluation for a daycare center in Sunnyvale. The daycare center is located downgradient and adjacent to several sources of volatile organic compounds in groundwater. The investigation included the collection of soil gas and indoor air samples to evaluate potential vapor intrusion concerns from the subsurface. The results of the investigation indicated that significant concentrations of volatile organic compounds were present in soil gas, but that indoor air samples have not indicated a significant impact from the subsurface. Additional soil gas and indoor air monitoring is being conducted to evaluate potential temporal effects on both vapor intrusion mechanisms and remedial efforts conducted for one of the potential source areas.
Vapor Barrier and Passive Ventilation System for Commercial Property
Project coordination for approval of a human health risk assessment for a site with residual concentrations of petroleum hydrocarbons in the subsurface. Due to the presence of benzene and methane in soil gas a combination vapor barrier and passive sub-slab ventilation system was proposed for the new commercial facility to be constructed over the chemical-affected area. The San Francisco Bay Regional Water Quality Control Board approved the risk assessment as well as the vapor barrier/ventilation system design. The vapor barrier and ventilation system have been installed and the building construction was completed. Testing of the system has confirmed the effectiveness of the system in allowing subsurface vapors to vent from below the foundation through the system to ambient air above the building roof.
Subsurface Vapor Intrusion-Based Indoor Air Evaluation for Tetrachloroethene
Development and implementation of an indoor air evaluation for tetrachloroethene (PCE) in subsurface soil and groundwater in Lodi, California. As part of the Cleanup Order from the Central Valley Regional Water Quality Control Board, an indoor air evaluation of potential vapor intrusion of PCE and other associated volatile organic compounds from the subsurface to indoor air was evaluated by collecting indoor air samples and ambient air samples. The data was used to estimate potential indoor air excess cancer risks and noncancer hazards and evaluate prioritization of subsurface investigation activities and remedial measures.