Superfund Innovative Technology Evaluation (SITE)
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
Inc., Freeze Barrier Technology September 2004
SITE Technology Capsule (540/R-03/508a)
Arctic Foundations, Inc. (AFI), of Anchorage, Alaska has developed a freeze barrier technology designed to prevent the migration of contaminants in groundwater by completely isolating contaminant source areas until appropriate remediation techniques can be applied. With this technology, contaminants are contained in situ with frozen native soils serving as the containment medium. The U.S. Environmental Protection Agency's (EPA) Superfund Innovative Technology Evaluation (SITE) Program evaluated the technology at the U.S. Department of Energy's (DOE) Oak Ridge National Laboratory facility in Oak Ridge, Tennessee from September 1997 to July 1998.
For the evaluation, an array of freeze pipes called "thermoprobes" were installed in a box-like structure around a former waste collection pond. The thermoprobes were installed vertically to a depth of 32 feet below ground surface and anchored in bedrock. The 'thermoprobes were connected to a refrigeration system by a piping network. A cooled refrigerant (R404A) was circulated through the system to remove heat from the soil. When the soil matrix next to the pipes reached 0 �C, soil particles bonded together as the soil moisture froze. Cooling continued until an impermeable frozen soil barrier was formed.
After the barrier wall reached its design thickness of 12 feet, the groundwater level within the former pond dropped, indicating that the barrier wall was effective in impeding recharge into the former pond. Further, water levels collected from within the former pond did not respond to storm events compared to water levels collected from locations outside the containment area, indicating that the barrier wall was effective in impeding horizontal groundwater flow through the former pond. Finally, a 1996 groundwater tracing investigation showed groundwater transport from the former pond area in a radial pattern which was not the case during the demonstration groundwater tracing investigation.