Vapor Intrusion Mitigation Design, Installation & Operations

Challenge & Solution

Rhea was contracted to design, install, monitor, and operate a vapor intrusion mitigation (VIM) system at a federal government facility in North Carolina. The facility contains a former fuel farm site that is being remediated. Air sparging and biosparging remediation activities related to the former fuel farm resulted in hydrocarbon vapors seeping into a building at the government facility.

Rhea was contracted to monitor the vapors and provide a remedial solution to both remove vapors from the building and prevent their continued intrusion.

Project Description & Highlights

The goal of this project is to reduce vapor levels within the building to levels below maximum limits approved by base industrial hygiene personnel and/ or the Environmental Management Department (EMD).

Rhea monitored the hydrocarbon vapors surrounding the building as well as potential “hot spots” inside the building.  Based on our knowledge of the site coupled with gauging and free phase product thickness determinations within the area, Rhea provided a design for a vapor intrusion mitigation (VIM) system to recover hydrocarbon vapors within the slab and below grade to prevent vapors from entering the building on site.

Rhea installed a network of vapor extraction points surrounding the building.  These vents were fitted with high efficiency radon fans which created a significant vacuum source which served to draw vapors from beneath the building and actively prevent their intrusion into the breathing zone.

Several of the vent borings were installed at depths that not only removed vapors from below the building but are actively aiding in the further remediation of the former fuel farm area.  In addition, Rhea sealed potential migration points within the building.

Within one week of the VIM system start up, hydrocarbon vapor levels inside the building decreased to below maximum limits approved by the federal government’s industrial hygiene personnel. 

VIM systems are relatively inexpensive and easy to maintain, thus the installation of a VIM system will save our client money by allowing for continued use of the building. 


North Carolina