Phase 2 focused feasibility study report for the reduction of mercury in plant effluent project at the Oak Ridge Y-12 Plant, Oak Ridge, Tennessee

The purpose of this focused feasibility study (FS) is to review the alternatives that have been evaluated under the Reduction of Mercury in Plant Effluent scoping efforts and provide justification for the recommended alternative. The chosen option from this study will be executed to meet the mercury-specific requirements of the recently negotiated National Pollutant Discharge Elimination System (NPDES) Permit for the Oak Ridge Y-12 Plant. Four previous ``mercury use`` buildings at the Y-12 Plant have been identified as primary contributors to these discharges and are scheduled to undergo upgrades to mitigate them as sources. They are 9201-2, 9201-4, 9201-5, and 9204-4. These buildings contain mercury-contaminated pipes and sumps that discharge to EFPC. The current requirements for limiting mercury discharges to EFPC are defined in the draft Y-12 Plant NPDES Permit, which is expected to become effective in July 1994. The main requirement related to mercury in the permit is to reduce the downstream mercury concentration to 5 g/day or less. Three basic options are considered and estimated in this study, including treatment at the building sources with local units ({approximately}$3.8 million); a combination of local treatment and centralized treatment at the Central Pollution Control Facility ({approximately}$6.6--8.9 million); and hydraulic control of the groundwater and/or in situ soil treatment ({approximately}$120 million). As negotiated under the NPDES Permit, an ``interim`` local unit, utilizing carbon adsorption, is being placed in operation in the 9201-2 building by July 1994. Since the major uncertainties associated with meeting the NPDES permit discharge requirements for mercury are flow rates and treatment efficiency, the 9201-2 unit will provide within 6 months the data necessary to optimize a treatment design