Part One in a series on Tokyo Underground, produced with content from the following Magnesium members:
Photography © Ken Lee and Skorj / Magnesium All Rights Reserved
Text  © Skorj / Magnesium All Rights Reserved

Only a few man-made structures lend themselves to automatic inclusion in science-fiction movies. Locations so out-of-this-world they have to be used as phantasmagoric shooting locations. San Diego’s Geisel Library, half the Statue of Liberty, the Bradbury Building…

On the Northern outskirts of Tokyo, the list also includes a drain. Also known by the fabricated name “G-Cans” (not an abbreviation of anything in particular), the Metropolitan Area Outer Underground Discharge Channel however is no ordinary drain, but a series of enormous, interconnected, underground facilities. Massive holding tanks, surge suppressors, huge pump rooms, networked tunnels, control rooms, inlets, outlets, overflows, and more – all fifty meters underground.

With one hundred kilometers of flood control tunnels, the overall project was started in 1992, with the G-Cans section finishing in 2009. Designed to provide flood control for the northern reaches of the greater Tokyo metropolis, the G-Cans element alone is massive on an unimaginable scale.

Photography: Ken Lee / Magnesium. Nikon F100 35mm and XP2 Super.

The two billion dollar G-Cans project is nearly six and a half kilometers long, with an interconnecting series of holding silos, varying in size up to sixty-five meters tall and over thirty meters in diameter. The largest holding tank is the massive “cathedral” – one hundred seventy-seven meters long and seventy-seven meters wide. Its roof is supported by sixty massive pillars, designed to provide both strength and low resistance to the swirling waters.

The basic design function of G-Cans is to re-channel potential flood waters from one watercourse to another, balancing and regulating the water flow to ensure flood surges and river breaches are kept to a minimum. As well as natural water flows, a turbine hall, equipped with ten megaWatt of Pratt & Whitney pumping capacity, can move over two hundred thousand liters of water per second into the adjacent Edo River. That’s enough water to fill an Olympic-sized swimming pool in just over one second.

Photography: Skorj / Magnesium.

Construction of the main tunnels utilized a conventional Tunnel Boring Machine (“TBM”) and a two-layer lined tunnel – supporting framework and internal smooth sleeves for water flow. Ground water freezing was undertaken with large-scale expander insertions into the surrounding rock, with condensate forming on their many coupling heads, the now-removed expanders resembled alien spawning stations.

Standing meters below the previous high-water mark, with the sound of compressors and dripping water in the distance, is a remarkably surreal experience. The damp languid air adds to the feeling of potentially being swallowed up by a flooding wave as it careens through the tunnels, sweeping everything to its doom along the way. Fifty meters below the surface, fifty meters below the suburbs, with the kids playing soccer on the fields of Saitama above our heads, riding bicycles through the tunnels as we explored really added to the off-world feeling.

Since completion, the tunnels, side chambers, and main “cathedral” hall have been used in making a Tetsujin 28 film, a Range Rover commercial, numerous other TV spots, and some of the photographs here were used in the source rendering for a computer game.

While the main tunnels are now off-limits for access, the control room, above-ground infrastructure, and main cathedral are sometimes available for tours during the non-typhoon season. Bookings are available for Japanese speakers via their main website.

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