Soil vapour extraction (SVE), also known as "soil venting" or "vacuum extraction", is an in situ remedial technology that is primarily used to reduce concentrations of volatile constituents of petroleum products adsorbed to soils in the unsaturated (vadose) zone. This technology applies a vacuum through in ground wells near the soil contamination. The more volatile compounds within the contaminant plume volatilise and the vapours are drawn towards the extraction wells. Extracted vapour is then treated as required (often by carbon adsorption) before being released to the atmosphere. The increased flow of air, most particularly oxygen, through the subsurface soil also stimulates the biodegradation of some of the contaminant compounds. Wells can be installed either vertically or horizontally, depending on site conditions. In areas where the groundwater table is high, water draw down pumps may be required to balance the effect of water upwelling induced by the vacuum system.

Suitability

This technology has been proven effective in reducing concentrations of volatile organic compounds (VOCs) and certain semi-volatile organic compounds (SVOCs) found in petroleum products at storage sites. SVE is generally more successful when applied to the lighter (more volatile) petroleum products such as petrol. Diesel fuel, heating oils, and kerosene, which are less volatile than petrol, are not readily removed by SVE, nor are lubricating oils, which are considered to be very much non-volatile. Almost all petroleum products are biodegradable to a certain degree and so these heavier petroleum products may be suitable for remediation by bio-venting. Injection of heated air also can be used to enhance the volatility of these heavier petroleum products because vapour pressure generally increases with temperature.

SVE may also be appropriate near a building foundation to prevent vapour migration into the building. Here, the primary goal may be to control vapour migration and not necessarily to remediate soil.

Please call or e-mail to discuss the applicability of this technique to one of your sites.