Windrow composting is being successfully used at full scale to remediate soils contaminated with high explosives (HE) as part of the Pantex Plant Environmental Restoration (ER) Project in Amarillo, Texas. The project (OST/TMS ID 1529), supported by Accelerated Site Technology Deployment, involves systematic soil removal and treatment to decrease the HE concentration to a nonhazardous level. Subsequently, the soil is disposed of in Pantex’ on-site Environmental Landfill Cell.

The Pantex Plant manufactured conventional weapons during World War II and subsequently converted to the assembly and disassembly of nuclear weapons. Scrap HE and HE-contaminated components generated during these processes were dispositioned through controlled detonation and burning at the Pantex Burning Grounds, leaving soils contaminated with HE and barium nitrate.

The windrow composting facility consists of two 270-foot-long modular structures, each with the capacity to house three windrows (so called because the long mound shape resembles hay raked in preparation for baling). Each windrow treats approximately 100 cubic yards of contaminated soil at a time. Key factors contributing to the design and construction of the project were effectiveness and cost, so basic goals were identifying optimal amendments and using easily obtainable and relatively inexpensive resources. The project adopted several strategies to meet these goals:

• procuring locally available equipment to construct the modular facility;
• using locally available materials for composting, such as steer manure from a local feedyard and second-cycle wood chips from a municipal composting operation;
• adding mycelium from white rot and other fungi to increase the efficiency of HE mineralization; and
• using sulfate-based fertilizers as terminal electron acceptors for microbial metabolism and chemically converting soluble barium to relatively insoluble barium sulfate.

Jay Childress, the ER Soil Remediation Section manager responsible for the Pantex HE Composting Technology project, says, "By March 2000, we treated about 3,500 cubic yards of HE-contaminated soil. The cost of composting is about $82 per cubic yard, compared with somewhere around $396 per cubic yard for disposing of the soil as Class I waste. Using this technology, we estimate that we saved DOE over a million dollars."

The clear reduction in treatment, disposal, and transportation costs has prompted plans for expanded application of this innovative technology in FY 2001. Plans are under way to compost the approximately 10,000 cubic yards of contaminated soil contained in ditches on the Pantex site. Also, as a result of the demonstrated savings, export of the technology to other DOE sites such as Los Alamos National Laboratory is being considered for curbing long-term liability costs for the DOE Environmental Restoration Program.

For more information on the Pantex HE Composting Technology Project, contact Martin Amos at (806) 477-6458, mamos@pantex.com.