Tokyo’s vast underground temple-drains: the G-Cans

MJG Catacombs / Caves, Haikyo, Tokyo-to 15 Comments

The G-Cans Underground Temple in Saitama is probably the most massive underground flood management system in the world- comprised of 100s of kilometers of tunnels up to 50 meters underground connecting 5 vast silos and one immense water tank: The Temple. The complex spans 6.3km between Showa in Tokyo and Kasukabe in Saitama, with the power to pump 200 tons of water per second into the Edogawa river. Wow.

Image from here.

This complex- known as the ‘Underground Temple’ for its towering pillars and cavernous scale- is actually free for tourists to visit and photograph. I wanted to go but they only have opening hours on weekdays, and will only allow you on the tour if you speak Japanese- so you can heed directions in the event of an emergency. My Japanese skill is only luke-warm, so I decided to take a virtual Google Image tour instead.

Image from here.

Construction on the Temple began in 1992 and only finished this year- costing around $2 billion. It seems like a huge amount of money for an anti-flooding project- especially as all the rivers are already paved with concrete and bulwarked with giant tetrapods, flood-plains, and levy-mounds. Does Tokyo really require such extreme defensive measures?

Image from here.

According to Tokyo’s Central Disaster Management Council, if rainfall totaling 550 millimeters over three days hits Tokyo, causing the Arakawa river in Kita Ward to overflow its banks, then up to 97 subway stations would be flooded. That is however a once-in-200 years event, but one that G-Cans would help to drain away. See here for more details.

Image from here.

It’s probably impossible to say whether this whole thing is very wise and prescient, or just another huge hunk of candy handed down to the construction companies from the pockets of the politicians. I suppose only catastrophic flooding will tell the tale- if such a once-in-200 years event occurs, the planners will be touted as seers and their works emulated all around the world..

Well, good for them. Sometimes you just have to spend the tax-payers (my!) yen.

Image from here. .

Image from here. .

Image from here. .

Image from here. .

Image from here. .

Image from here. .

Image from here. .

Image from here. .

Image from here.

G-Cans has managed to make a little money on the side from film and commercial shoots: here’s a Range Rover ad that was shot in the Temple:

If you’re interested in visiting G-Cans- here’s the website where you can book a place on the tour.

FACTFILE

Location – Tokyo / Saitama Entry – By tour, Tues to Thurs, only with J-speaking guide. Facts – Started 1992, finished 2009, $2 billion, Highlights – Being massive and looking awesome, underground.

TOKYO

You can see all MJG’s Tokyo content here:

[album id=5 template=compact]

Comments 15

  1. I found out about G-Cans a few months ago and was thoroughly blown away. That colossal size reminds me of a part of the Blade Runner game, but to know that this thing is real is absolutely incredible. I’m determined to visit some day…

  2. Definitely a place I would go to while here or somewhere to take your mates if they are looking for something not Tokyo .
    Kinda reminds me of the movie ‘Total Recall’ – the end scene when Arnie enters the mines and discovers some huge machine.

    It was also featured on tv sometime in February the people going round were those who kept on saying ‘dekai’ and ‘sugoi’ they totally wet themselves.

  3. A tour eh? Too bad we couldn’t go there ourselves and just walk around. Knowing Japanese tours, they’d probably be pretty restrictive in where you could go and what you could do.
    Very interesting though, another great waste of taxpayer’s yen!

  4. Well, don’t blame MMLee. He may not know about this. But after knowing will he deliberate with his smart people, whether he should embark on tnis massive project.

  5. As suggested, development conceived also for bomb shelter. Can be harnessed to use river water for usage instead of recycling used water from homes/sewage system which is much more expensive and healthy.

  6. As suggested, development conceived also for bomb shelter. Can be harnessed to use river water for usage instead of recycling used water from homes/sewage system which is much more expensive.

  7. Pingback: “In Case Of Emergency” | Dead End Thrills

  8. I read an article that stated Tropical Storm Lee (2011) dumped 45 trillion gallons of rain over Eastern US. (170 cubic kilometers). If something like that, or a series of storms stalled over Tokyo long enough, G-cans or not, Tokyo would be a waterworld. Japan’s largest lake, Lake Biwa, only holds 27.5 km3, 1/6th of a major storm, so yeah, its not a waste of money, its necessary. Too bad other cities do not have the equivalent…yet…

  9. The idea is very simple and there is no reason why it shouldn’t work. All the Japanese did was to simply rely on gravity to let the excess water flow down the underground openings and then let it drain off to the sea on its own via huge underground pipes,
    If we in Singapore can even construct a deep massive underground tunneling system for our sewage, I cannot see why it can’t be similarly done for our rainwater drainage.
    In fact, rainwater drainage needs much fewer branchings of the pipes and need not be as water-tight as sewage pipes, and so the cost would be very much less than building the sewage pipes.
    The underground rainwater pipes can also be utilised for harbouring people in times of war.

  10. I know your article predates the Tohoku earthquake, but I still think it’s relevant to contrast the following point. This G-Cans site is engineered for a two hundred year event, whereas the Tohoku earthquake is considered a once in a thousand year event. Yet still people lament that the destruction should’ve been avoided with better engineering! Sadly where I’m originally from, the town recently suffered a disaster from a fifty year flood. Clearly there’s a point in between that needs to be settled on. I don’t think an island nation, with a heavy rainy season and propensity for tsunamis is over-preparing for a two hundred year event.

Leave a Reply

Your email address will not be published. Required fields are marked *