The removal of volatile and semi volatile contaminants in vapour phase and the reduction of adsorbed phase contaminants within the vadose zone.

Vacuum applied to wells installed through the contaminated zone induces airflows through the subsoils thus stripping vapour phase contaminants directly from soil pore spaces. The application of vacuum to the subsoils reduces air pressures below ground rendering previously less volatile compounds more volatile. This increasing the range of contaminants removable to include less volatile compounds. Clean air recharging into the treatment zone increases the supply of oxygen to the area thus enhancing biological activity providing further remediation of less volatile contaminants.

The vacuum extraction process can readily be applied to large areas of a site and with careful design can be tailored to control and remove a broader range of contaminants. Though generally considered suitable for more porous soils, hi-vac technology can be used in more cohesive soils.