Tokyo Underground

The Construction Series > Earthquake >Small > Ginza > Circular > Earth > Underground

If someone refers to the Captain as “going underground,” the typical connotation is that of the sleuth snooping through a seedy burg or random less-than-reputable establishment. Certainly his exhaustive survey last week of the Lip and Hip “high quality touch club" in Kabukicho, where shrewd negotiation cut the entrance fee by two-thirds, would be a perfect example.

But this week the Captain is literally heading under Tokyo’s surface, 40 meters to be exact. Glance over his shoulder as he inspects a massive Tokyo utility project that purports to be making the city a safer and more enjoyable place.

It is a typical central Tokyo intersection. Office workers shuffle out of coffee shops; cheap suit outlets troll for customers with fancy window displays; taxis and buses clog the roads from curb to median; and a construction site - as all intersections in this modern metropolis seemingly require - sits on one corner, white fencing surrounding the property.

But this intersection in Toranomon is special in a particular way: no column, scaffold, concrete mixer, or other standard evidence of work ever shows itself from behind the construction site's enclosure. The reason can be found below - way below - ground level.

Stepping past the barrier and descending a narrow spiral staircase to a temporary platform reveals Tokyo's literal underworld. It is a stunning 20-meter diameter concrete cylinder extending down for 40 meters. Light green hues reflecting off the smooth concrete from mounted lights fill the scene as workers move in and out of a temporary trailer and up and down the single steel-cage elevator.

The project, titled the Azabu-Hibiya Common Utility Duct is a public works venture under the Ministry of Land, Infrastructure and Transport that collects various utility lines into a single trunk tunnel. Not only are Tokyo¹s endless streams of overhead wires slowly being reduced as a part of an effort to decrease earthquake susceptibility, the stunning scene makes for a unique tourist attraction.

A report provided by the Tokyo National Highway Office said that after the 7.3-Richter magnitude Kobe earthquake in 1995, which killed more than 6,000 people, similar ducts tended to move along with earth pressures and suffered little damage.

The existence of a single underground "lifeline" during these times, the Ministry says, will increase the chances that vital services will continue to be supplied at the time of the disaster. By contrast the Kobe quake resulted in utility services going down. As well, emergency vehicles being restricted access to troubled areas by downed and entangled utility lines.

The Japanese Cabinet office's Central Disaster Management Council issued a report in December 2004 indicating that a major earthquake in Tokyo could result in 13,000 deaths and the destruction of 850,000 buildings.

A 2004 study by the Earthquake Research Committee indicated that there is a 70 percent chance that Tokyo will be hit by a major tremor within the next 30 years. The Great Kanto Earthquake of 1923 was the last large quake to strike Tokyo. About 140,000 people died amid falling buildings and subsequent fires.

Over 100 kilometers of roadway in Tokyo have been given similar treatment. Under Route 246, a completed duct that stretches from Aoyama to Akasaka has been in operation for 20 years. Plans are set for an additional 1,000 kilometers throughout the metropolis.

Public works projects are typically shrouded in secrecy. But this project is different.

"A lot of Japanese citizens have this idea that public works projects are not for the public,” says Kiyotaka Yamana, who under the Tokyo Geo-Site Project promotional moniker arranges public tours and encourages general awareness. “They (public works projects) are notorious for having negative images attached to them. I am trying to let the public know why they exist and what they are being used for."

By presenting these concrete works as fully open tourist attractions, Yamana can show the public that taxpayer money is not literally being flushed down the drain.

During the two-hour tours, held a few times each year, visitors strap on protective helmets and walk through a section of a completed segment. The experience is similar to entering a science fiction movie set; machines clank and hum as visitors proceed down illuminated concrete arteries that appear to continue forever.

Colorful displays and placards along the path tell the story of how the work has been performed. A handful of the workers are on hand to answer questions.

Yamana is always looking for “friendly” events to attract visitors. Traditional Japanese theater performances have been staged on a makeshift stage atop the bottom of the shaft. As well, votive lights have been strewn along the tunnel floors to create candlelit walks. Included among the visitors to this subterranean world have been television crews and film-makers.

With the public associating public works with past financial busts like the Aqualine toll expressway - one of many recent examples of bureaucrats citing inflated demand projections to justify large project budgets - Yamana is trying to develop a sense of openness to a practice that has typically been very opaque.

"Once people have a chance to visit, a lot are amazed with what is inside, the size of the space, the machines that are used, and the people who are doing the work," Yamana explains.

Toranomon is the "launching shaft." The cylinder is a hub in which lateral utility tunnels emerge at its bottom in the directions of Azabu and Sakuradamon.

Theses tunnels are concrete-lined by rings of reinforced concrete blocks, slightly curved to fit into place around the walls. A large slurry tunneling machine, with rows of teeth affixed to a rotating shield, bores its way laterally through the generally sandy soil at a diameter that ranges from five to seven meters.

The reinforced concrete blocks (about the size of the tops of office desks) are pushed into place by jacks attached to the back of the machine to form one ring of the lining. Subsequent rings are added as the work, which follows the centerline of the road above, continues laterally from the hub. . Two hours is required to install a single ring.

A scaffold is then mounted slightly above the bottom of the tunnels. In addition to providing a floor on which workers can move, a center rail allows a train, named “Pikachu,” to haul the blocks and various bits of needed construction equipment as the work progresses along the line.

The utility lines - such as gas, telephone, water, electric, and cable - are designated by a specific color, are affixed along the walls.

As the name implies, the project extends from the Tokyo districts of Azabu to Hibiya. Toranomon is roughly in the center. Construction, which began in 1989, was recently completed for the 2.8-kilometer segment between Azabu and Toranonon. The additional 1.5 kilometers for the Hibiya segment is expected to be completed by 2010. The project’s budget is 42 billion yen, which corresponds to roughly 10 billion yen per kilometer of road.

The number of workers required is minimal. Only four are needed to operate the boring machine, while the site might include 25 in total at any given time.

Work was delayed at Hibiya for a short period in 2001 when a pile driven below the surface for the construction of a retaining wall discovered 240 stones from the Hibiya Gate of Edo Castle.

Digging for the Hibiya segment started last year. The work has extended a little more than 800 meters, nearly reaching the moat of the Imperial Palace. This distance contains a slightly uphill slope to a depth 30 meters below the surface. For reference, the Yurakucho subway line crosses nearby at about 15 meters below the surface. In later stages, the work will take a ninety-degree turn at the moat and continue another 580 meters to Hibiya.

Other benefits of the project include: the disappearance of overhanging lines makes the metropolis more pleasing to the eye; utility line longevity is increased by the lack of exposure to natural elements; and the reduction in costly excavation eases maintenance and increases pedestrian and vehicle flow.

"In central Tokyo, a lot of road construction is taking place, causing traffic jams,” Yamana says. “Here, a common utility tunnel is being placed under major areas so that if one cable is cut off or some other problem happens, a workman can go underneath and do the repair work without having to dig a trench."

In neighboring Saitama prefecture, Yamana likewise promotes the Metropolitan Area Outer Discharge Channel under the G-Cans Project title. This project, however, differs slightly in scope from its Tokyo public works brother.

This 6.3-kilometer network is a series of inlets, pumps, and massive underground concrete channels that funnels rainfall runoff into the Edogawa River before it empties into the Pacific Ocean.

For this project, Yamana has expectations that reach beyond mere tours and theater shows; he wants to show the world the appeal of Japan’s concrete spectacle.

Spectacular pictures of large support columns and meandering channels contained on the G-Cans Project Web site have caught the attention of Life magazine and ABC News (Australia). Yamana hopes Hollywood comes calling next.

"My dream,” he says, “is for the next 'Die Hard' movie to have Bruce Willis jogging through one of the concrete channels.”

Sweet concrete dreams…

Note: All photos taken during a tour of "The Azabu-Hibiya Common Utility Duct."

The Construction Series > Earthquake >Small > Ginza > Circular > Earth > Underground

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