The weapons production reactors were decommissioned at the end of the Cold War, and decades of manufacturing left behind of high-level radioactive waste stored within 177 storage tanks, an additional of solid radioactive waste, and areas of heavy Technetium-99 and uranium contaminated groundwater beneath three tank farms on the site as well as the potential for future groundwater contamination beneath currently contaminated soils. In 2011, DOE, the federal agency charged with overseeing the site, "interim stabilized" 149 single-shell tanks by pumping nearly all of the liquid waste out into 28 newer double-shell tanks. Solids, known as salt cake and sludge, remained.