Environmental engineers use pneumatic fracturing extraction and hot gas injection to treat in situ contamination located within low permeable formations (Accutech Remedial Systems, Inc. 1994). The process has been demonstrated at numerous sites and significantly increases subsurface permeability and contaminant mass removal (U.S. EPA 1993b). The process applies controlled bursts of high pressure air into a well through a proprietary injection and monitoring system. When the down-hole pressure exceeds the pressure of the formation, channels or fractures are created propagating from the fracture well. Once the permeability of the formation is increased, engineers inject hot gas air (250 to 300°F for pilot-scale and 300 to 600°F for full-scale design) under pressure to elevate the temperature of the fracture surface and volatilize contaminants located within the formation matrix. The extracted vapors are then treated by activated carbon during low-concentration process streams or by catalytic technology during high-concentration process streams.
The technology can be applied at depths to 50 feet and has a radius of influence of as much as 40 feet from the injection point (well). Subsurface air flow has been increased 150 times compared with the site's natural permeability. The technology, however, is not applicable for treating inorganic or nonvolatile organic compounds. In addition, applying the pneumatic fracturing process may be unnecessary at a site with a high natural permeability.
Was this article helpful?