Service: Vapor Intrusion Mitigation

Once contamination is released to the ground, it poses a threat not only to groundwater but also to human health. One of the common mechanisms of exposure to this threat is vapor intrusion to indoor spaces by volatile compounds such as solvents and light fuels like gasoline. Once it is determined there is a health threat from vapor intrusion, several factors and options can be considered to mitigate the health risk in indoor environments. These considerations vary depending on when the risk is identified (before or after building construction), whether the occupied space is a residence, workplace or other use and the design of the building.

The Reynolds Group has extensive experience with several technologies used to protect human health from risks associated with vapor intrusion. Some examples include engineered solutions like sub-slab membranes, sub-slab depressurization, passive venting and ventilation and HVAC system integration.

PCE Sub-Slab Depressurization (7715)

Client: ARIZONA CIRCLE PARTNERS
Proj Mgr: Tabitha Esther
Completed: In Progress
Industry: Metal Finishers
Real Estate Managers/owners
Service: Vapor Intrusion Mitigation
Soil Vapor Extraction
This project in Los Angeles involves a building that formerly housed a metal plating shop. The processes involved with the plating operations used PCE (a chlorinated solvent that readily volatilizes) and released it into the soil beneath the site. Soil vapor surveys and assessments have identified the threat to the health of the occupants of the building due to the intrusion of PCE vapors into the building. Following a site inspection, the Reynolds Group performed a pilot study to determine the applicability of sub-slab vapor intrusion mitigation to protect the occupants from exposure to PCE.

Because the release and subsequent human health threat occurred after the building was constructed, the options for mitigating vapor intrusion were limited. The buildings slab-on-grade construction further limited the options. Through the pilot study, TRG demonstrated that applying a vacuum (depressurization) to the interface between the bottom of the concrete slab and the soil immediately beneath it, PCE vapors could be captured and prevented from entering the building. TRG then designed a simple and practical depressurization system to be installed to protect the workers at the facility from the human health risk.

Passive Ventilation of Methane (7172)

Client: PRIMESTOR DEVELOPMENT
Proj Mgr: Al Fuan
Completed: In Progress
Industry: Real Estate Developers
Service: Vapor Intrusion Mitigation
Sometimes, the threat of vapor intrusion is associated with naturally occurring compounds such as methane. Dangers associated with methane include explosive environments and asphixiation at higher concentrations. In areas where methane is known to exist in the subsurface, engineered barriers are part of the building design requirements.

TRGs client, a major shopping center developer, built a large retail center and needed to mitigate the possibility of methane intruding into the buildings of the center. A passive sub-slab venting system was designed and installed during the construction of the shopping center. The vapor intrusion mitigation program requires periodic monitoring of methane concentrations. TRG regularly performs these site visits at minimal cost to the management of the property.

Benzene Air Exchange Rates (6626)

Client: PACIFIC SOUTHWEST GROUP
Proj Mgr: Dwayne Ziegler
Completed: 03/15/2005
Industry: Real Estate Managers/owners
Service: Vapor Intrusion Mitigation
While developing a site for a senior living facility, TRGs client encountered soil and groundwater impacted with gasoline. The contaminated groundwater was flowing from a gasoline station uphill from our clients construction site. Among the various issues presented by the migrating gasoline contamination was the concern of intrusion of benzene into the residences. Benzene is a component of gasoline and can off-gas from groundwater. In a vapor phase, benzene can then intrude into indoor environments.

Several options were available to address the concern, but the most cost effective was to use the design of the proposed facility and not add to the cost of the project. The senior apartments were to be built over subterranean parking. Parking garages are required to have ventilation systems in place to mitigate carbon monoxide associated with vehicle exhaust. TRG was able to show that the ventilation system of the garage would adequately mitigate the residents exposure to benzene from the contaminated groundwater. This approach saved the project thousands of dollars in changes.
Environmental Consulting & Environmental Contracting
Environmental Consulting & Environmental Contracting
Environmental Consulting & Environmental Contracting
Environmental Consulting & Environmental Contracting