The U.S. Department of Energy (DOE) prepared this environmental assessment (EA) to analyze the potential environmental impacts associated with the proposed interim measures for the Mixed Waste Management Facility (MW) groundwater at the Burial Ground Complex (BGC) at the Savannah River Site (SRS), located near Aiken, South Carolina. DOE proposes to install a small metal sheet pile dam to impound water around and over the BGC groundwater seepline. In addition, a drip irrigation system would be installed. Interim measures will also address the reduction of volatile organic compounds (VOCS) from ''hot-spot'' regions associated with the Southwest Plume Area (SWPA). This action is taken as an interim measure for the MWMF in cooperation with the South Carolina Department of Health and Environmental Control (SCDHEC) to reduce the amount of tritium seeping from the BGC southwest groundwater plume. The proposed action of this EA is being planned and would be implemented concurrent with a groundwater corrective action program under the Resource Conservation and Recovery Act (RCRA). On September 30, 1999, SCDHEC issued a modification to the SRS RCRA Part B permit that adds corrective action requirements for four plumes that are currently emanating from the BGC. One of those plumes is the southwest plume. The RCRA permit requires SRS to submit a corrective action plan (CAP) for the southwest plume by March 2000. The permit requires that the initial phase of the CAP prescribe a remedy that achieves a 70-percent reduction in the annual amount of tritium being released from the southwest plume area to Fourmile Branch, a nearby stream. Approval and actual implementation of the corrective measure in that CAP may take several years. As an interim measure, the actions described in this EA would manage the release of tritium from the southwest plume area until the final actions under the CAP can be implemented. This proposed action is expected to reduce the release of tritium from the southwest plume area to Fourmile Branch between 25 to 35 percent. If this proposed action is undertaken and its effectiveness is demonstrated, it may become a component of the final action in the CAP. This document was prepared in compliance with the National Environmental Policy Act (NEPA) of 1969, as amended; the requirements of the Council on Environmental Quality Regulations for Implementing NEPA (40 CFR 1500-1508); and the DOE Regulations for Implementing NEPA (10 CFR 1021). NEPA requires the assessment of environmental consequences of Federal actions that may affect the quality of the human environment. Based on the potential for impacts described herein, DOE will either publish a Finding of No Significant Impact (FONSI) or prepare an environmental impact statement (EM).