Well Injection Depth Extraction (WIDE) System
The Well Injection Depth Extraction (WIDE) system is a hybrid soil flushing/soil vapor extraction system that uses Prefabricated Vertical Wells (PVWs) in lieu of conventional wells or sumps to extract groundwater and inject liquid flushing agents. The PVWs are installed at relatively close spacing (less than 3 feet apart) to shorten groundwater drainage paths and accelerate the soil flushing process. Surface treatment, such as Air Stripping, Granular Activated Charcoal (GAC), and Ion Exchange are used to treat extracted groundwater and soil gas.
The WIDE system has successfully extracted trichloroethylene (TCE), uranium (U), and technetium-99 (99Tc) from the subsurface. Under extraction-only operation, volatilizing TCE from the soil enhanced TCE removal.
Injection of liquids through PVWs, with concurrent extraction, was found to increase groundwater extraction flow rates and enhance the removal of dissolved contaminants.
Limitations and Concerns
The WIDE technology is predominantly a shallow depth (less than 30 feet) remediation system. Although wells can be installed to depths greater than 90 feet, vacuum extraction of liquids is limited in practice to depths of approximately 30 feet.
At the Ashtabula site, the system experienced icing problems at temperatures below 30 degrees F.
When the system is used to extract dissolved contaminants by flushing, there is concern that the system will merely dilute the contaminant without extracting it from the groundwater. Thus robust monitoring is needed during operation.
The technology is adapted for use in tight soils such as fine clay. This system is a removal enhancement. It has been field tested for the removal of dense nonaqueous phase liquids (DNAPLs), light non-aqueous phase liquids (LNAPLs), and dissolved contaminants such as uranium in soil and groundwater.
Technology Development Status
Researchers from North Carolina State University developed the WIDE system. The Department of Energy has stated that the system is ready for deployment and commercial application.
Other Resources and Demonstrations
The WIDE system was demonstrated at a DOE uranium manufacturing site in Ashtabula, OH. The groundwater and soils are contaminated with TCE, U, and 99Tc as a result of long-term uranium manufacturing operations. The field-scale demonstration of the WIDE system included a grid of over 480 PVWs installed to a depth of 15 ft. The system used vacuum extraction to remove the TCE-contaminated groundwater and soil gas, which in turn was treated in an above-ground treatment system. The site’s existing wastewater treatment plant was used to treat the radioactive constituents.