The Oak Ridge Reservation (ORR), consisting of approximately 37,000 acres of Federally-owned land, is located in Oak Ridge, Tennessee on the Clinch River downstream of the Melton Hill Dam and near the confluence of the Clinch River and Poplar Creek. In the early 1940s, the United States Department of Energy (DOE) constructed three major facilities on the ORR. Operated for research, development, and processes in support of the Manhattan Project, these facilities include the Oak Ridge National Laboratory (ORNL), Oak Ridge Y-12 Plant, and East Tennessee Technology Park (ETTP; formerly Oak Ridge K-25 Site). The ORR and associated facilities comprise the Site. Activities at Site facilities have resulted in the discharge of hazardous substances (e.g., polychlorinated biphenyls [PCBs] and mercury) and radioactive compounds, leading to the contamination of natural resources both at the Site and in the surrounding environment, including adjacent waterbodies.