ISOCELL for Removal of Contamination

ISOCELL^™

Removal of Contaminated Soils, Mixed Waste or Unexploded Ordnance

This patented technology allows the safe removal and offsite treatment of contaminated soil/groundwater, mixed wastes or unexploded ordnance. Examples of applications include:

Coal tar contaminated soil.
High level radiation contamination.
Mixed wastes such as landfill debris and radiation contamination.
Soft sludge and sediments from mixed waste treatment ponds.
Unexploded ordnance and other sensitive materials.

This ground freezing technology consists of freezing the entire contaminated soil/groundwater mass at the site. The perimeter of selected smaller blocks of this frozen mass (approximately 5' to 10' square) is then thawed out slightly and the frozen block is removed from the ground with a crane. This frozen block can then be coated with a protective film and/or insulation and transported offsite for treatment or disposal.

Advantages of ISOCELL^™ Ground Freezing for Contamination Removal

Works in All Ground Conditions—This technique will work just about anywhere a steel freeze pipe can be installed. This includes running sand, cobbles, peat, soil mixed with debris, clay, etc. Freeze pipe can be moved or additional pipe installed if refusal is encountered in debris. Because freezing penetrates far into all materials, exact placement of freeze pipe is not essential.

Reduces Instability and Criticality—The cooling effect of ground freezing significantly reduces volatility and instability of most materials. It also solidifies very soft or sticky materials such as sludge or tar. At mixed waste sites involving high level radiation, the freezing process with greatly reduce potential criticality.
Increases Worker Safety—The contamination or unexploded ordnance is locked into place with the freezing process. This reduces the risks to worker from air vapors or accidental explosions. Releases to the environment are also reduced. Moreover, the freeze pipe installation can be accomplished using remote methods such as robotics, thus reducing risks to workers even further.
Flexible Installation—The small diameter of our freeze pipe (typically about 3 inches) allows them to be installed around virtually any size or shaped obstruction (debris, ordnance, etc.) in the ground. Geophysics or other method to identify the size, shape and depth of the obstructions are important for us to place the freeze pipe as close to the obstruction as practical. Various types of freeze pipe installation methods are available, depending on the subsurface conditions. These methods include: auger drilling, mud rotary drilling, driving, vibrating and pushing.
Cost Competitive—Our freezing systems are very efficient and have been found to be cost competitive with other types of retrieval technologies. In many cases, we are likely to be the least costly method. Costs depend on site conditions, site size and other factors.

Step 1—Pipe and Lifting Assembly Installation

Steel freeze and thaw pipes are installed in the ground in a grid pattern.
A lifting assembly capable of lifting a specified mass of soil is embedded in the unfrozen soil. Lifting eyes may be made part of the freeze pipe units (as shown above).
The ground is completely frozen (thaw pipes are off) to solidify the soil, groundwater and contamination.

Step 2—Selective Thawing around Frozen Soil Blocks

Thaw pipes are activated around one block of frozen soil (typically 5' to 10' in plan) to create a weak zone of soil at the thawed zone interface.
Uplift pressure is applied on the block using hydraulic rams attached to the lifting assembly.
The frozen block is lifted a few inches out of the ground after the frozen bonds are broken. The block is allowed to refreeze to a hard state again.

Step 3—Complete Removal of Frozen Block from the Ground

After the frozen block is allowed to refreeze overnight and the block is completely removed from the ground using a suitably sized crane.
The block can then be sprayed with a mist of water that freezes as a seal on the frozen soil. Insulation can also be sprayed on the block to prevent thawing during transport.
The frozen block is now ready for transport on a truck or train car. For short distance trips (less than one day), refrigeration is not needed. For long distance trips, it may be necessary to ship the frozen block in a refrigerated container.

Photograph of an ISOCELL^™ demonstration project.
The frozen soil block and freezing assembly is shown during Step 2 with the block partially removed from the ground.

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