OK, so, in a community fortress my friends and I have been running, I built a big fountain monument in our (walled outdoor) meeting area. There was water that fell from sort of stone gantry down onto a number of floor grates and statues. The falling and impact with the statues and the like generates mist, while the dwarves happily hang out there and enjoy themselves.
The water then falls through the floor grates to a reservoir immediately below from which it is pumped back up into the gantry for re-use. It was great. Golden statues, silver floor grates, inlaid stone floors surrounding them, etc etc.
Until winter came. Our map only freezes for a short period, but all the water in the gantry and in the part of the reservoir that was exposed to the air (the bit below the grates) was frozen solid, while any water that had not fallen through became icy floor. No problem really, the dwarves continued using the meeting area and statue garden and waited until the thaw to get the fountain working again.
But when the late-winter thaw happened, my game lagged out for five seconds, and then the monument exploded, tossing six dwarves (including a noble who liked bins and a master brewer 
) and a stray donkey into the water formed by the instantly unfreezing ice blocks.
I didn't really know what had happened, until I looked into the water to find my silver grates lying forlornly on the bottom. They had, I presume, somehow become encased in the ice (despite being floor tiles on the square above the ice - they had been showing the # symbol through the winter) and been de-constructed. Whether that happened when they were frozen and I missed it, or when they thawed, I don't know. This strikes me as rather bug-like, because firstly thaw shouldn't happen in a split second, but that's a much more complicated issue than just this bug. What I'm really bug-repping here is that constructed floor grates above an ice-filled square become deconstructed either during freeze or thaw. Which doesn't seem right.
When I get back to my desktop PC at home tonight I can post screenshots, but I don't have a save from when it occurred, only one from a year later when I handed the reins over to the next of my friends. I drained the reservoir, gave the dead a proper burial and then renovated the monument. The water now falls an additional Z-level to a lower reservoir, from which it is pumped back up into the main reservoir faster than it can fall. The result is that there is never enough water directly below the grates to cause ice tiles to form there, and the grates stayed constructed through my second winter.
Of course, one of my mates could overfill the reservoir by not decoding my intricate set of levers, pumps and floodgates correctly and things will explode again, but that's the fun of a community fortress. If we couldn't put the "Collapse The Dining Room" lever next to the "Raise the Drawbridge" one, where would the fun be?
Ninja edit: Long post is long. TL;DR version: water freezes below floor grates, grates deconstructed when ice thaws, dwarves drown.
[ March 13, 2008: Message edited by: Narmio ]
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Topic: [33g] Exploding fountain kills six, film at 11. (Read 709 times)