Metropolitan Area Outer Underground Discharge Channel
The Metropolitan Area Outer Underground Discharge Channel, popularly known as G-Cans, is an underground water infrastructure project in 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 and diameters of, connected by of tunnels, beneath the surface, as well as a large water tank with a height of, with a length of, with a width of, and with fifty-nine massive pillars connected to seventy-eight pumps that can pump up to of water into the Edo River per second.