DGSI. Durham Geo Slope Indicator


Control valve facilitates the passive removal of vapors from the unsaturated soil zone.


Passive Soil Vapor Extraction (PSVE) and in situ bioremediation

The Baroball is a valve that makes it possible to harnesses natural atmospheric pressure fluctuations to create a pumping method that passively removes vapors from the unsaturated soil zone (Passive Soil Vapor Extraction). (View an illustration of the barometric pumping process with Baroball.) This technology has been demonstrated to increase removal rates by up to 50%. Natural atmospheric pressure fluctuations are transmitted through the unsaturated subsurface resulting in pressure differential between the surface and subsurface. When the zones are directly connected by a well placed in the vadose zone, the pressure differentials will result in flow into or out of the well.

Simply put, the Baroball is a check valve that is installed at the top of the well casing to permit gas flow in one direction. The Baroball has been used in conjunction with the FAP Plus systems to increase removal rates during LNAPL recovery. Other applications include the final polishing for an active SVE system where removal rates have been substantially reduced to the point where SVE system operation costs are very high. Inverted Baroball installations have been used to allow air flow into the subsurface, but prevent air escape to improve in-situ bioremediation.

The Baroball has also been used to provide plume control of methane production at landfills.

Model Description


Standard Baroball for soil gas extraction


Inverted Baroball for atmospheric air injection


For more information

Brochure (PDF 200 KB)
Passive Soil Vapor Extraction (PSVE) for VOC Remediation at the Metallurgical Laboratory (MetLab) June 2005 Progress Report Brian D. Riha (June 2005)
Metallurgical Laboratory (MetLab) June 2005 Progress Report", report nr WSRC-TR-2005-00268



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