: The Metropolitan Area Outer Underground Discharge Channel (首都圏外郭放水路)
: Saitama-ken (埼玉県)
: 720 Kamikanasaki, Kasukabe city, Saitama 344-0111 (〒344-0111 埼玉県春日部市上金崎７２０)
: 048-747-0281 (Mon - Fri 9:00-16:30)
: Every Tuesday to Friday - Morning tour 10:00 - 11:30 & Afternoon tour 14:30 - 16:00 (maximum 20 participants per tour)
: From Minami Sakurai station (南桜井駅) in Kasukabe, on the Tōbu Noda Line - Google map here
The Metropolitan Area Outer Underground Discharge Channel (also called The G-Cans project
, in Japanese 首都圏外郭放水路 Shutoken Gaikaku Housui Ro
), is a huge underground infrastructure located mostly in Saitama-ken, which was built for preventing flooding of the capital during rainy and typhoon seasons.
The project was initiated in 1992. It consists of 5 concrete containment silos with a height of 65 meters and a diameter of 32 meters, located close to 4 major rivers and connected by 6.4 km of tunnels. Should there be too much water in those rivers, those silos can absorb a huge amount of water from the rivers. Those silos are connected by pipes 50 meters beneath the surface, together with a large water tank called "The Cathedral", with a height of 25.4 meters, a length of 177 meters (!), and a width of 78 meters. Should this place, too, be filled, 10 MW pumps can pump up to 200 tons of water per second (!) into the Edogawa River, located at a lower altitude. See the picture above for more information... Or this flash animation
Even better, this G-Cans project is also a hidden tourist attraction which can be visited for free - but tours are only in Japanese, so bring someone who can translate.
For more information and online reservation : Details of the tour (in English)