During excavations from 2004 to 2007, a sample of purified plutonium was uncovered inside a safe in a waste trench, and has been dated to about the 1940s, making it the second-oldest sample of purified plutonium known to exist. Analyses published in 2009 concluded that the sample originated at Oak Ridge, and was one of several sent to Hanford for optimization tests of the T-Plant until Hanford could produce its own plutonium. Documents refer to such a sample, belonging to "Watt's group", which was disposed of in its safe when a radiation leak was suspected.