Quote:

http://www.masstransitmag.com/news/12347762/barts-rising-floodwaters-wreaked-rush-hour-havoc
June 28--A rush-hour delay caused by flooded tracks at the Powell Street Station in San Francisco -- in the middle of summer -- points up a BART issue that doesn't get nearly the attention that overcrowded trains, finicky air-conditioning and the seemingly daily "equipment problems" command: a steady supply of subterranean water.
Groundwater moving through downtown San Francisco's sandy soil en route to the bay leaks into the subway between the Embarcadero and 16th Street Mission stations. It seeps through cracks and joints in the tunnel walls, creating a steady drip-drip-drip and even trickling like a mountain stream in places.

One of those places is the southwest end of the Powell Street Station. And that's where a drain that funnels the water into the sewer system clogged with debris at just the wrong time, Monday evening's rush hour.

Soon, water was pooling a foot deep on the eastbound trackway and rising rapidly toward the third rail. Since water and electricity don't mix well, BART halted trains heading toward the East Bay outside the station about 5:45 p.m. while it sent workers in to unclog the drain.