A french kid was metal deteching and set off part of a shell.

[Sunray]

"...keep the UXB guys going for 100 years..." The French(their Department of Mine Clearance disposes of about 900 tons of unexploded munitions every year.) and Belgians have special units who do nothing but dispose of ordnance dug by farmers. Isn't just HE either. They're digging up W. W. I vintage gas shells, hand grenades, bombs assorted and every other type of ordnance. Reuters figures there's another 100 years worth of W.W. I munitions alone. The USAF and RAF dropped 2.7 million tons of bombs between 1940 and 1945 on Germany alone.
And that doesn't include the assorted training areas. There's a W.W. II CF training area north west of here that was used as an Army Cadet Summer camp and militia training for eons. We were not allowed to use any of the bush due to UXB stuff. One of my Cadets found a mortar round sticking out of the ground.