Improved apparatus for high vacuum groundwater extraction

There is provided an apparatus for removing contaminants from a contaminated area of the ground having a water table and a vadose zone above the water table which comprises a perforated riser pipe (44) extending downwardly a vacuum extraction pipe (30) situated inside of the riser pipe (44) and having a bottom opening situated within the perforated riser pipe (44) said vacuum extraction pipe (30) being capable of containing groundwater prior to application of a vacuum thereto said vacuum extraction pipe (30) having at least one gas inlet (41d 41e) in the vacuum extraction pipe (30) for introducing a gas into the vacuum extraction pipe (30) to initiate two-phase flow within the vacuum extraction pipe (30) a riser pipe gas inlet (31) for introducing a gas into the riser pipe (44) a vacuum-forming apparatus in fluid communication with the vacuum extraction pipe (30); and adapted to form a zone of reduced pressure in the ground around the riser pipe (44) whereby gases and liquid can be drawn from the ground into the riser pipe (44) and from the riser pipe (44) into the vacuum extraction pipe (30) and conveyed to the surface as a two-phase common stream and a means for receiving the common stream and separating the stream into separate gas and liquid streams characterized in that at least two gas inlet openings (41d 41e) are provided in the vacuum extraction pipe (30) wherein the supply of gas to each gas inlet opening is controlled through a common gas inlet tube (41) wherein the diameter of the first gas inlet opening (41d) situated uppermost in the vacuum extraction pipe is less than the diameter of all gas inlet openings situated beneath said first gas inlet opening (41d); and wherein the diameter of each additional gas inlet opening other than the first gas inlet opening (41d) is greater than the diameter of all gas inlet openings situated above said additional gas inlet opening.