State and federal agencies asked a federal judge Wednesday to approve a new cleanup schedule for the Hanford nuclear reservation, the nation's most polluted nuclear weapons site.

The motion filed by the U.S. Department of Energy and the state Department of Ecology would govern the complicated cleanup of underground storage tanks for the next four decades and allow federal courts to ensure the work is completed.

"This will ensure our continued progress as we work to meet our commitments to the state of Washington to protect the environment, the public and the Columbia River," U.S. Energy Secretary Steven Chu said in a statement.

A watchdog group opposed the decree, saying it delays cleanup work for too long.

Hanford stores over 53 million gallons of radioactive and chemical waste in 177 underground tanks, many of which have leaked. The material is left over from the production of plutonium for nuclear weapons, and Hanford workers have already spent two decades on cleanup.

The new schedule envisions four more decades of work, which provides thousands of good-paying jobs in the Tri-Cities area of Richland, Kennewick and Pasco.