The Metropolitan Area Outer Underground Discharge Channel (Japanese: 首都圏外郭放水路, Hepburn: shutoken gaikaku hōsuiro), is an underground water infrastructure project in Kasukabe, Saitama, Japan. It is the world's largest underground flood water diversion facility, built to mitigate overflowing of the city's major waterways and rivers during rain and typhoon seasons. It is located between Showa and Kasukabe in Saitama prefecture, on the outskirts of the city of Tokyo in the Greater Tokyo Area.
Work on the project started in 1992 and was completed by early 2006. It consists of five concrete containment silos with heights of 65 metres (213 ft) and diameters of 32 metres (105 ft), connected by 6.4 kilometres (4.0 mi) of tunnels, 50 metres (160 ft) beneath the surface, as well as a large water tank with a height of 25.4 metres (83 ft), with a length of 177 metres (581 ft), with a width of 78 metres (256 ft), and with fifty-nine massive pillars connected to seventy-eight 10 MW (13,000 hp) pumps that can pump up to 200 metric tons (200 long tons; 220 short tons) 200 tons of water into the Edo River per second.
- Sheer, Jon (n.d.). "Metropolitan Area Outer Underground Discharge Channel". AFAR. ISSN 1947-4377. OCLC 1054388800. Archived from the original on 22 April 2021. Retrieved 11 May 2022.
- Zolbert, Alex (1 November 2012). "How giant tunnels protect Tokyo from flood threat". CNN. Tokyo. Archived from the original on 8 March 2022. Retrieved 11 May 2022.
- "G-Cans: Tokyo's Massive Underground Storm Drain".
- "G-Cans Project, Kasukabe, Saitama, Greater Tokyo Area, Japan". Retrieved 10 January 2015.
|Wikimedia Commons has media related to Metropolitan Area Outer Underground Discharge Channel.|
- Official website (including photos) (in Japanese)