25 years of environmental remediation in the general separations area of the Savannah river site: lessons learned about what worked and what did not work in soil and groundwater cleanup - 15270
The Savannah River Site, which is owned and administered by the US Department of Energy, covers approximately 900 square kilometers. The General Separation Area is located in the center of the site and includes: radioactive material chemical separations facilities, radioactive waste tank farms, radioactive seepage basins, and the radioactive waste burial grounds. Radioactive wastes were disposed in the General Separation Area from the mid-1950's through the mid-1990's. Operations at the F Canyon began in 1954 and at H Canyon began in 1955. Waste water disposition to the F and H Seepage Basins began soon after operations started in the canyons. The Old Radioactive Waste Burial Ground began operations in 1952 to manage solid waste that could be radioactive from all the site operations, and ceased receiving waste in 1972. The Mixed Waste Management Facility and Low Level Radioactive Waste Disposal Facility received radioactive solid waste from 1969 until 1995. Environmental legislation enacted in the 1970's through 1990's led to changes in waste management and environmental cleanup practices. The US Congress passed the Clean Air Act in 1970 and the Clean Water Act in 1972; the Resource Conservation and Recovery Act was enacted in 1976; the Comprehensive Environmental Response Compensation, and Liability Act was enacted by Congress in 1980; and the Federal Facilities Compliance Act was signed into law in 1992. Environmental remediation at the Savannah River Site essentially began with a 1987 Settlement Agreement between the Savannah River Site and the State of South Carolina. The site manages several of the larger groundwater remedial activities under the Resource Conservation and Recovery Act for facilities recognized early on as environmental problems. All subsequent remediation projects are managed under a tri-party agreement (Department of Energy, Environmental Protection Agency, and South Carolina Department of Health and Environmental Control) through the Federal Facilities Agreement. Environmental remediation activities during the past 25 years have stabilized and capped seepage basins as well as consolidated and capped waste units and burial grounds in the General Separation Area. Groundwater activities include: pump and treat systems in the groundwater, installation of deep subsurface barrier systems to manage groundwater flow, in situ chemical treatments in the groundwater, and captured contaminated groundwater discharges at the surface for management in a forest irrigation system. Concentrations of contaminants in the aquifers beneath the General Separation Area and in surface water streams in the General Separation Area have decreased over the past 25 years. Closure of 65 waste sites and 4 Resource Conservation and Recovery Act facilities has been successfully accomplished. Environmental clean-up has progressed to the stage where most of the work involves monitoring, optimization, and maintenance of existing remedial systems. Many lessons have been learned in the process of remediating the General Separations Area. Geo-textile covers outperform low permeability clay caps, especially with respect to the amount of repairs required to upkeep the drainage layers as the caps age. Passive and enhanced natural processes to address contamination are much more cost effective than pump and treat systems. Forest irrigation can be very effective in water management situations with non-accumulative contaminants such as tritium and volatile organic contaminants. (authors)