An agreement has been reached to clean up the radioactive K West Basin on the Hanford Nuclear Reservation, the nation's most polluted nuclear weapons production site.

The deal was announced Tuesday between the U.S. Environmental Protection Agency and the U.S. Department of Energy, which owns Hanford.

The settlement involves the Energy Department's failure to meet a September 2014 deadline to begin removing sludge from the K West Basin.

A new deadline for starting the removal of sludge was set at Sept. 30, 2018. The removal of sludge must now be completed by Dec. 31, 2019.

Hanford is near Richland, Washington, and for decades made plutonium for nuclear weapons. The site is now engaged in a decades-long process of cleaning up radioactive waste left by that work.