Henderson said the alert was raised early Tuesday after employees at the Plutonium Uranium Extraction Facility (PUREX), a former chemical processing plant located at the center of the site, noticed during a routine inspection that soil had sunk over one of two tunnels in the area.
Nowhere in the United States is there more nuclear waste and radioactive contamination than at Hanford, which has been the focus of a massive, complex cleanup effort by the U.S. Department of Energy since 1989.
The collapse took place at the intersection of two tunnels used to store contaminated equipment since the 1950s, the statement said.
Hundreds of workers at the Hanford nuclear waste site in Washington state have been ordered to "take cover" after a portion of a tunnel appeared to collapse. Obviously, there's concern for nearby water sources, but at this time, no injuries have been reported.More news: Putin undecided which song to play when he meets Trump
Hanford Emergency Center spokesman Destry Henderson says that the area near the cave-in was evacuated and non-essential workers were at first told to stay indoors, and then allowed to go home. Hanford, which sits next to the Columbia River, was one of the original Manhattan Project sites. Constructed decades ago, the walls of the older tunnel are 14 inches thick and held up by pressure-treated Douglas fir timbers arranged side by side, the report said. Crews were still surveying the site and about 3,000 employees in the area were still being told to take shelter, as they had all morning. The Energy Department has said there is no evidence showing workers have been harmed by vapors.
"No action is now required for residents of Benton and Franklin counties", the Energy Department said, referring to the almost 300,000 residents near the site about 200 miles southeast of Seattle.
Heeter said that the greatest threat presented by plutonium is airborne contamination.
A tunnel near the site contains several rail cars that have been temporarily buried because they were used to transport irradiated fuel rods and remain contaminated.
Hanford for decades made plutonium for nuclear weapons and is now the largest depository of radioactive defense waste that must be cleaned. That same year, six tanks at the site were found to be leaking radioactive waste. It's estimated that almost two-thirds of the plutonium used by the USA government during Hanford's lifespan - and a staggering amount of related waste - was produced at this one site. But after more than 20 years and $19 billion dollars, not a drop of waste has been treated.