Federal energy officials are permanently closing two underground storage tanks that once held radioactive liquid waste from nuclear weapons production at the Savannah River Site in South Carolina near Augusta.
They're the first such tanks closed at the site in 15 years.
The tanks, built during the height of the Cold War, once held enough radioactive waste to fill two Olympic-sized swimming pools.
Now, six cement trucks will arrive every hour -- eight hours a day, five days a week, for the next five months -- to fill them with grout, closing them off for good.
While Undersecretary for Nuclear Energy Thomas D'Agastino hailed the closures as a milestone, the tanks also are only the third and fourth tanks -- out of 51 total -- that need to be made safe at SRS.
"This will put us in good position to start accelerating the closure rate," D'Agastino says. "So, this isn't a matter of 'Every 15 years two tanks get closed.' This is a matter of 'The tip of the iceberg.'"
A US Department of Energy timeline has the next four tanks being closed by 2015 and all SRS tanks being closed by 2028.
"These two tanks provide proof, in principle, that we now understand what it takes to move forward to get these tanks closed out and get the regulatory pieces completed," D'Agastino says. "And we're now in a position to apply that, frankly, to these other facilities."
The agency has been working to clean up the two tanks in question since the 1980's.
An Energy Department official estimates the total cost to taxpayers -- for these two tanks alone -- at $50 million.
The official says that the costs to close the remaining tanks will be significantly less.