Mercury Management in the Oak Ridge Reservation - 22062

The U.S. Department of Energy (DOE) Oak Ridge Reservation (ORR) is located within and adjacent to the city limits of Oak Ridge, Tennessee and is under the purview of the DOE Oak Ridge Office of Environmental Management (OREM). The ORR hosts three major industrial research and production campuses originally constructed as part of the World War II-era Manhattan Project: the Heritage Center (formerly the K-25 site then East Tennessee Technology Park); the Oak Ridge National Laboratory (ORNL); and the Y-12 National Security Complex (Y-12). OREM, along with the Tennessee Department of Environment and Conservation, and the U.S. Environmental Protection Agency, have identified mercury contamination at Y-12 as the greatest environmental risk on the ORR. Efforts over the last 25 years to reduce mercury levels leaving the site in the surface waters of Upper East Fork Poplar Creek (UEFPC) have not resulted in achieving acceptable mercury concentrations in fish throughout the creek. Mercury continues to be released into the UEFPC from discrete and diffuse sources within Y-12. Mercury enters UEFPC from direct erosion of contaminated soil, migration of dissolved mercury through storm drains and several outfalls, and through shallow groundwater. Within Y-12, the West End Mercury Area consists of former mercury use buildings, contaminated soils, and contaminated sewers in the immediate vicinity. Residual mercury in the seventy-plus year-old deteriorating storm drain infrastructure, infiltrating groundwater, and sediment-bound mercury are remobilized and transported through the storm drain network and daylight through Outfall 200 into the UEFPC. Outfall 200 is the integration point for storm sewer effluent entering UEFPC; and under dry weather (base) flow conditions is consistently the largest single source of mercury to the creek. During 1998-2000, DOE prepared Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) Remedial Investigation and Feasibility Study documents for the UEFPC Characterization Area focused on potential source units (i.e. areas of soil contamination and groundwater plumes) that could contribute to the transportation of contaminants within and from the Characterization Area. In 2002, the UEFPC Characterization Area Phase I Record of Decision (ROD) (DOE 2002) was signed, outlining future cleanup activities. DOE has implemented a series of projects that have reduced the concentrations of mercury measured at the site boundary Station 17, the Y-12 National Pollutant Discharge Elimination System (NPDES) permit compliance point. While mercury concentrations at Station 17 have declined, the concentrations continue to exceed the surface water concentration goal specified in the UEFPC Characterization Area Phase I ROD. This paper will focuses on the details and progress of a centrally located water treatment facility for mercury removal which is a key component of the mercury cleanup strategy. This facility, referred to as the Outfall 200 Mercury Treatment Facility, is currently under construction and will serve multiple purposes by assisting in the reduction of mercury in the headwaters of the Upper East Fork Poplar Creek, and support future demolition and remediation activities of former mercury use facilities. (authors)