Hidden below the Tokyo streets is a true superhero – a bitumen-washed facility with state-of-the-art technology and an architectural beauty to put a Corbusier or two in the shade. This is G-Cans, also known by the unlikely name of Metropolitan Area Outer Underground Discharge Channel.
But it’s not just a pretty face! It’s an underground water storage tank, part of a titanic floodwater diversion facility. This is the biggest reservoir, but it’s not the only one. It’s the culmination of a series of five huge silos with a connecting tunnel extending over 6 kilometres.
I’ll try to explain the system simply for anybody interested. The outskirts of Tokyo to the north are criss-crossed with rivers and streams. In times of heavy rainfall, this densely urbanized zone has always been subject to extensive flooding, very costly to deal with. A solution had to be found, and this is it.
Beyond this last reservoir is the Edo River. On the other side are the silos – interconnected of course. These absorb floodwater from the other rivers in the surrounding area and gradually feed it down through the tunnel to the storage tank where we stand.
The water flows relatively slowly towards this reservoir, to be stored then gradually pumped into the Edo River by 14,000-horsepower turbines.
In fact the facility is only in use between June and November, roughly between the rainy and the typhoon season.
The rest of the time, the site is open to the public and entry is even free. But there’s no denying access is difficult from Tokyo and there’s little else to visit nearby.
By the way, after you’ve seen the exhibition and video, the actual tour is extremely short. You’re only allowed to explore the inside of the storage tank for ten minutes.
All the photos posted here were taken in that time. Best be prepared! 🙂
And this is the only entrance (and exit) to the “Underground Temple”. Imagine all that really lies beneath our feet, especially in the big cities …
For security reasons, visitors must speak Japanese or be accompanied by someone who does. You also need to book well in advance via the official website. For more information visit the G-Cans English page.