Yes this was not uncommon, all kinds of shit was put into hescos. Unless an area was specifically swept for mines (time consuming, expensive and labor intensive) it was usually randomly selected topsoil.

I was/(am?) a bomb tech, I didn't dig up a damn thing, we were too highly valued of an asset..And only having a small handful of us to support an entire theater of war makes us exceedingly rare.

Got called out on quite a few. One in particular was a dude out at a COP in the middle of no where Farah, taking a piss next to a Hesco, looked up and saw a mine poking out of the barrier. Afghanistan is one of the most heavily mined countries in the world. It's not surprising.