The building I work in, the CUE, was flooded last week. At first it seemed like a boneheaded failure lead to mass destruction – but it was actually a subtle design fault exposed by rare circumstance that led to the flooding. A steam event happened in the basement. The entire campus is steam heated, so these are common. A pop off valve either opened or was broken and allowed the steam to vent through a chimney-like structure to the roof. This is as designed. Due to high winds, however, the steam was blown under the fascia covering the HVAC equipment on the roof. The steam heated the underlying ceiling of the penthouse to the point that a sprinkler head in an air plenum popped off, dumping ~4000 gallons of water into the plenum.
At this point the fire alarm went off due to the sprinkler dump. The water was trapped in the plenum, and the sprinkler head was not on any of the maps the firefighters had access to. A firefighter broke through a wall and discovered the flooded plenum. Once the determination was made that there was no fire, the sprinklers were shut off. By then, it was way too late. I do not fault the firemen for waiting so long to disable the sprinklers; had there been a fire it was clearly the right thing to do to let them dump.
At this time a lot of the water had escaped through the walls and floor of the plenum, flooding the elevator shaft, the penthouse, parts of the fifth floor and parts of the fourth floor. The ceiling in the main conference room failed and a lot of AV equipment was damaged or destroyed. Sheetrock walls were destroyed as were lots of carpet. The true costs will not be known for some time, but it was an amazing cascade of co-incidence that allowed this failure to happen. They’re going to extend the steam vent above the fascia to prevent it from happening in the future.