[lepton]

...but how many of the shells detonate on their own?

Is the battlefield actually dangerous assuming one doesn’t go banging on rounds with a sledgehammer?

Sequestering chemical rounds is still probably a good idea.

[virgil]

I think I read somewhere that at the Ypres battlefield there are underground piles of explosives that were meant to be exploded along the German line, that were placed there by sappers during the war, and never detonated or removed. Back in the 1950s one of caches detonated due to a lightning strike, and it was a huge explosion. There still one other cache that they know about.

[Pontiac]

This year alone, some 500 tonnes of shells have been removed from the ground, and are currently being stored until they are disposed of by way of controlled explosion.

I wonder how long they store these explosive shells.

TNT becomes less stable with age. One shell stored with dozens of others self detonates setting off the others would be bad.

[Paratrooper]

Visited the battlefield with my dad in 1958, it was still dirt and dead trees with barbed wire strewn about. We dug in the dirt finding bullets and ended up getting slightly gassed from ruminant chemicals in the dirt...never forget my eyes burning and tearing.

[FLT-bird]

Farmer’s plows have been known to hit and set off unexploded ordnance resulting in horrific injuries and/or death.