(CRYOCELL®)
CRYOCELL® is a barrier system which provides real-time monitoring capability, earthquake resiliency, and diffusion-free full enclosure contaminant isolation. The system is repairable in situ and removable upon completion of containment needs.
CRYOCELL® design involves installing an array of freeze pipes, using standard well-drilling equipment, which surround the contaminated source or groundwater plume much like the ribs of a canoe. Once installed, the array of freeze pipes is connected to freeze plants by a distributive manifold and supplied with cooled brine at a design temperature of -10 °C to -40 °C to freeze the volume of soil between the pipes, resulting in a 12- to 16-foot barrier.
The barrier's thickness and temperature may be varied through design to match containment requirements. If no subsurface confining impervious layer is present, the array can be installed using an angled or "V"-shaped configuration beneath the contaminated zone, completely enclosing the site. If additional barrier thickness is a design requirement, a parallel array of freeze pipes is installed in staggered spacing outside the first array. This configuration allows the entire inner volume of soil between the two arrays to be frozen, thereby increasing barrier thickness per design up to 75 feet. The depth of the containment envelop can be in excess of 500 feet.
CRYOCELL® engineering is site-specific and considers many cost-related factors, including waste type, topography, soil conditions, thermal conductivity, and groundwater movement. A computer program incorporates all site characteristics into a three-dimensional model that engineers use to establish the most efficient design and estimate the cost of CRYOCELL® for a specific site.
A thick frozen soil barrier offers a number of advantages for confining hazardous waste. The barrier does not degrade or weaken over time and is repairable in situ. If ground movement fractures the barrier, the fissures can be filled and resealed quickly. Maintenance costs are extremely low, allowing continued use for extended periods. In addition, the frozen barrier is environmentally benign. When the site is decontaminated, the frozen soil is allowed to melt and the pipes are removed. The technique is an alternative to conventional containment systems using steel, concrete, slurry walls, or grout curtains. The figure illustrates two typical containment systems.
RKK, Ltd. (RKK), reports that CRYOCELL® can provide subsurface containment for a variety of sites and waste, including underground tanks; nuclear waste sites; plume control; burial trenches, pits, and ponds; in situ waste treatment areas; chemically-contaminated sites; and spent fuel storage ponds. CRYOCELL® is designed to contain all known biological, chemical, or radioactive contaminants. Frozen soil barriers are adaptable to any geometry; drilling technology presents the only constraint.
RKK reports that the technology can isolate sensitive areas within large active operations (for example, sites within chemical and nuclear facilities), smaller raw material and waste management units (for example, tank farms, burial trenches, and waste treatment lagoons), and operational chemically contaminated sites, such as chemical plants, refineries, and substations. The technology can also contain a site or contamination during an in situ remediation project. It can also provide a redundant barrier for cut-off contamination processes, and reduces flow of groundwater into a contaminated zone.
Contaminants are contained in situ, with frozen native soils serving as the containment medium. Frozen soil barriers are impervious to chemical attack and are virtually impermeable at subzero temperatures. In addition, frozen soil barriers have great inertia, so they can remain frozen for as long as two years without refrigeration.
CRYOCELL® is economically favorable for intermediate- and long-term containment at large sites, and maintenance costs are extremely low. CRYOCELL® generates no waste streams or residues.
This technology was accepted into the SITE Demonstration Program in summer 1994. A treatability study was completed at the Department of Energy's (DOE) Oak Ridge National Laboratory in 1995. Results from the study are documented in a DOE Innovative Technology Summary Report, titled Frozen Soil Barrier Technology, and, Subsurface Contaminants Focus Area Technology Summary, (DOE/EM-0296), August 1996.
The RKK technology is being considered by DOE for use at other hazardous waste sites. RKK receives academic, technical, and scientific support through a cooperative and licensing agreement with the University of Washington.
EPA PROJECT MANAGER:
Steven Rock
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7149
Fax: 513-569-7105
TECHNOLOGY DEVELOPER CONTACT:
Ronald Krieg
RKK, Ltd.
16404 Smokey Point Boulevard, Suite 303
Arlington, WA 98223
360-653-4844
Fax: 360-653-7456
E-Mail: rkk@cryocell.com
Web Site: www.cryocell.com