Hanford Nuclear Site, Washington

Currently the most contaminated nuclear site in the U.S., the Hanford facility was established in 1943 on a 586 square-mile site, in order to produce plutonium for the top-secret Manhattan Project. In its heyday, the site included nine nuclear reactors, five plutonium processing facilities, and a host of laboratories, support buildings, storage tanks, etc., which facilitated the production of plutonium for the majority of the U.S.'s nuclear weapons. By the time the last of the nine reactors was shutdown in 1987, decades of plutonium production had generated more than 43 million cubic yards of radioactive waste, over 130 million cubic yards of contaminated soil and debris, 56 million gallons of highly radioactive waste stored in 177 underground tanks, and approximately 475 billion gallons of contaminated water, including over 200 square miles of groundwater. In 1988, the EPA divided Hanford into four separate Superfund cleanup sites, of which only the most minor (it contained no nuclear material) has been subsequently delisted, following cleanup. For a variety of reasons including funding and safety issues, mitigation efforts are behind schedule. Estimates of remaining cleanup costs are more than $113 billion, based on completion by 2060 with subsequent monitoring to continue until 2090.