New Yorkers will proudly tell you that the city has some of the finest tap water that you can find. But for nearly a century, all of Manhattan has been served by a single water tunnel that hasn’t been shut down for maintenance since it first opened in 1917. That’s no longer the case. The city has finally completed work on a water tunnel designed to provide some redundancy to Manhattan’s lifeline.

The tunnel runs 500 feet below the surface and is 12 feet in diameter. The section activated this week runs for 8.5 miles, serving all of Manhattan below Central Park. Ten separate shafts, each about a mile apart, use pressure alone to bring the water up to local distribution systems closer to the surface. Meanwhile, an earlier stage of the water tunnel completed in 1993 brings water 13 miles down from Yonkers, which lies just north of the city limits. In all a total of 82 million cubic feet of soil and rock has been removed from under the city — enough to fill Madison Square Garden 200 times. An astounding 30 million cubic feet of concrete has been poured to line the tunnels. A total of 24 "sandhogs," the term given to the men behind many of the city's legendary urban mining projects, have died to complete work on the latest tunnel.

Construction on this massive project to build Water Tunnel 3 (Tunnel 2 serves outer boroughs Queens and Brooklyn) has been underway, in fits and starts, since 1970. A total of $4.7 billion has been spent to bring a second water tunnel to Manhattan, with $2.7 billion of that funding coming under Mayor Bloomberg’s administration since 2003. That makes it one of the city’s largest public works projects ever.

But perhaps what’s most impressive is the system as a whole. The water that serves all of New York City comes from a number of reservoirs upstate. Aqueducts, some of which were built in the late 19th century, continue to provide water for the city. Water Tunnel 1, completed in 1917, was built with enough capacity that it remains completely sufficient today — the third tunnel was built for redundancy, not increased volume.

To announce the news, Mayor Bloomberg triumphantly gave a press conference from a massive valve chamber some 200 feet below Central Park. The soaring space has the presence of a cathedral — a place of worship for public works, if you will. Speaking of the water tunnel, he said "When I came to office, I asked what could literally close down the city. And the water tunnel could have really done that. I said, we have just got to make the investments." He added, "It's not sexy. And nobody says thank you." The third and final leg of Water Tunnel 3 remains to be completed. It’s set to provide redundancy in Brooklyn in Queens, which are both served by a single tunnel completed in 1936. The 10.5-mile long tube is expected to be completed in 2021.

Lead image credit: REUTERS/Mike Segar