So I have a cold zone where it's only warm enough to melt most of the river most years, once it melted all the way but usually it's cold, and I have a triple layer of aquifier.
I tried a cave in to get through it, but ended up having to channel during the times the water would run and then wait for a freeze then mine out the layer of ice and build walls and repeat for the next layer next season.
About 20 dwarves with their picks got ice cubed while trying to complete this multi year task, but that's not the face palm , not yet.
I finally get through and am happilly digging exploratory tunnels and find 3 layers of flux, I add steel making jobs and am busy doing other things, I get a job cancellation saying there was no flux,
I check the stocks menu, there is about 10 chalk right there, not forbidded, no restrictions on where my dwarves can go, everybody hauls... so I go to look at where my miners are digging, WTF? why is the tunnel flooding?
I look at my area where I dug through the aquifier, and I see two gaps in the walls and water is cascading into the pit and filling the tunnels.
Three miners are trapped, and I first build walls in the tunnel two dwarves do it right and are standing on the dry side the third dwarf has had three tries to do it right and every time walls himself off on the wet side.
I order him to mine more area starting with a diagonal so there will not be pressure problems, and after about 20 tiles he's too sleepy to continue and I have my other two dry dwarves try to build a rescue tunnel and they break through just as the wet one drowns, now they are wet too.
I start building stairs down , offsetting 1 tile every few layers so as the dwarves climb the wet stairs they do not plummet to their doom. and after some 20 levels down I break out into the cavern layer, and water is cascading out into the caverns now but there is food to be had here I set the miners to gathering and both of them find something to bring back to the newly staked out food stockpile, yup both of them found dimple cups, and are now hunting vermin and alternately trying to drink from the water cascading from the stairs Mechanic cancels drink: water sourse has dissapeared X196.
So my starving (cause they harvested dimple cups) and dehydrated (cause they can't drink from a firehose) and furious due to the preceeding two dwarves die, the baby one was hauling around is seen later playing in some GCS webs, the baby born a few days before this one turns into a child, and then this one dies.
I now look at the now refrozen walls the dwarves had cancelled the build walls task for some unknown reason, I try multiple times to build in thoes tiles to no avail, so end up building around the two tiles.
<head shake and face palms all around>