Hudson River, New York
The Hudson River is one of the nastiest major waterways in the U.S., and in 1984 a 200-mile stretch of the river, from Hudson Falls to New York City, received Superfund status. Due to the huge scope of this cleanup, the river has been called the largest Superfund site in the country.
The river's main issue is polychlorinated biphenyls (PCBs), dumped by manufacturing facilities on the Upper Hudson run by General Electric from 1947 to 1977. The PCBs have been linked to severe contamination of fish, enough to cause rapid evolutionary change in some species. Humans can be harmed just by contact with contaminated water, with potential health risks ranging from lower IQ to cancer.
Recreational fishing in the river has been banned due to the contamination, and water polluted with PCBs can no longer be used for agricultural purposes.
The Hudson River Superfund cleanup is one of the most aggressive efforts ever proposed to revive a polluted river, and has reportedly cost General Electric more than $1.5 billion to complete. Since the cleanup began in 2009, about 2.75 million cubic yards of sediment have been removed, including 310,000 pounds of PCBs — twice what was originally estimated.