The Hanford Nuclear Reservation was established by the United States in 1943 as part of the Manhattan Project on 586 square miles of land in south-central Washington. Columbia River borders the Site on the east and north. During the production of materials for nuclear weapons, the Site produced large quantities of wastes containing hazardous substances and radioactive materials. These wastes were managed by storing them on land and releasing them to ponds and ditches.

Over time, these wastes containing hazardous substances leaked and were released to the land, air, groundwater and surface water, including Columbia River. A preliminary accounting of these hazardous substances include: a variety of metals and radioisotopes and organic compounds including solvents, pesticides and PCBs. In 1988, U.S. Environmental Protection Agency placed Hanford on the National Priorities List and created four separate NPL sites: the 100 Area, 200 Area, 300 Area and 1100 Area. Production activities at the Site stopped in 1989 and work shifted to cleanup of the contamination which will continue for decades.

The Hanford Site has unique terrestrial and aquatic ecosystems that support at least 725 plant species, 40 mammal species, over 200 bird species and a variety of amphibians, reptiles and invertebrates. Columbia River, which borders the Site, supports economically and culturally important fish species such as Chinook salmon, coho salmon, steelhead, white sturgeon and Pacific lamprey.