For your viewing pleasure I have provided a link to a short but interesting video. It shows the disposal of large drums of wartime metallic sodium into a lake in Washington. It has that WWII news reel sound.
“Wartime sodium” in Washington suggests that the Na is from Hanford. Just a guess.
Thanks to Randy for the link.
Lamentations on Chemistry 
That was wonderful. Thank you, Gaussliing.
In grad school we often used sodium or potassium or liquid Na/K alloy to dry hydrocarbon and ether solvents. From time to time the distillation flasks containing multiple grams of these reactive metals needed to be cleaned. We would put the round bottom flasks (on a cork ring with a wide funnel in the neck) on the roof of the chemistry building and wait for the next rainstorm. Problem solved. Never got to see the pyrotechnics though.