This post is from my friend’s blog, but I thought that it was pretty amazing, amazing enough to repost.
I’m reading a book called Subterranean Twin Cities that talks about caves, sewers, and other underground things in the metro area. The largest storm sewer in the cities, called “Geyser Drain” by this book’s author, is a 5-mile-long y-shaped tunnel that runs 120 feet below the streets of Minneapolis.
One branch starts near Minnehaha Creek and eventually works its way under 35W before joining the other branch (originating in Loring Park) and discharging into the Mississippi. During periods of extreme rainfall, storm water backs up in the 14-foot-wide tunnel, rises up through 120-foot-deep vent shafts, and shoots out of holes in the median between the lanes of 35W. It’s pretty crazy.