Soil Vapour Extraction

Soil vapour extraction is a technology used in the remediation of soil, sediment, bedrock and sludge. It is also generically known as in-situ soil venting, in-situ volatilisation, enhanced volatilisation, or more commonly, soil vacuum extraction.

In simple terms it is the application of a vacuum through extraction wells to create a pressure gradient which induces gas phase volatiles to be removed from the soil.

The technology is an in-situ remediation of the unsaturated soil (Vadose zone) where a vacuum is applied to the soil to induce controlled flow of air together with volatile and some semi-volatile contaminants from the soil via the extraction points.

These extraction points are generally vertical wells carefully designed to produce an effective recovery route. However, some success can be achieved utilising horizontal extraction in shallower applications.

To further enhance the recovery process a geomembrane can be placed on the surface to increase the radius of influence of the wells. This will also assist in the prevention of preferential pathways being formed which can have a detrimental effect on the efficiency of the installed system.

In certain circumstances depression of the water table may be required as the application of a vacuum to the soil may induce a rise in the groundwater level. This groundwater lowering may also increase the depth of the Vadose Zone and thus improve the resultant remediation.

Soil vapour extraction is generally medium-to-long term in duration and can be used in association with air sparging technologies and/or pump and treat.