ABSTRACT
Vent wells can be fitted into boreholes similar to the way in which observation wells are installed. To prevent air from either entering or escaping in close proximity to the vent well, opening between the vent well and the borehole is sealed with bentonite. Volatile petroleum products can in general best be removed by applying the extraction mode. In addition to applying the extraction mode or injection mode, another option is to use a combination of injection and extraction. This design offers advantage of injection over extraction, it may allow greater well distances compared to extraction only and keeps the option of controlling off-gases, if necessary. Especially in winter time, soil air is relatively warm compared to the temperature at ground surface. This results in condensation of water in piping system which not only obstructs air flow but it also interferes with the sampling of soil gas from vent wells carried out to measure CO2 production or O2 consumption.
