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Japan's Subterranean Construction Boom

March 27, 1997

All over Japan, an underground construction boom has quietly gotten under way. Many different kinds of facilities are being built: not just the underground shopping malls that have long been a familiar fixture in this country, but a host of other structures including art museums, electric power plants, and dams. Previously, underground construction flourished during the years of Japan's bubble economy as land prices heated up and capital investment sought new outlets. The current boom, however, is motivated not by the high cost of above-ground real estate, but by the inherent safety, environmental, and technological benefits of subterranean spaces.

From Art Museums to Power Plants
In the hills on the outskirts of Takayama, a city in Gifu Prefecture, plans for construction of an underground art museum are in full swing. The plans call for tunneling into the bedrock, carving out a subterranean dome 40 meters in diameter and 20 meters high, and constructing a museum in that space. It will be connected to the surface by an entrance tunnel 13 meters wide, 8 meters tall, and 70 meters long. The museum is scheduled to open next April as what its developers call "Japan's first permanent display facility that utilizes subterranean space and is designed to accommodate a large number of people." Taking advantage of the constant temperature and humidity levels below ground, the museum will showcase a number of designated cultural properties, among them festival floats from the Takayama Festival and a famous taiko drum.

Meanwhile, in Yokohama, a new commercial district is being created, most of it underground. Known as Queen's Square Yokohama, the new district is part of a project aimed at developing an international cultural center on the Yokohama harbor waterfront, on a landfill site once occupied by a shipyard. Scheduled to open this summer, Queen's Square Yokohama will comprise three office buildings, a hotel, a department store, a concert hall, and other facilities. Over half of the floor area of these buildings (55%, to be exact) will be underground. And in a few years, a new subway line will open just below this district. When passengers exit the train, they'll be stepping right into an underground city.

High in the mountains near the city of Otsuki in Yamanashi Prefecture, the country's largest hydroelectric power plant is under construction 500 meters below ground level. The excavation will be 54 meters high, 34 meters wide, and 210 meters long, making it the largest subterranean space in Japan. The power plant is scheduled to be partially operational by July 1999.

In Okinawa, a place chronically plagued by drought, a subterranean dam is being constructed beneath a sugar-barley field in order to collect groundwater. The plans call for constructing a 55-centimeter-thick concrete dam that extends 60 meters below ground level to the clay that forms the floor of the water table and traps the ground water along a 2.5-kilometer stretch. The dam, being built on the coast near the city of Itoman, will be able to retain 3.4 million tons of water. Scheduled for completion in 2001, the project has attracted interest abroad; a succession of observers from the Middle East and other places have visited the site.

In Tokyo, a huge tunnel is being dug to regulate the flow of the Kanda River, which is prone to flooding during heavy rains. The river originates in the western suburb of Mitaka and flows through urban districts before emptying into the Sumida River in eastern Tokyo. The tunnel, 12.5 meters in diameter, is being dug 40 meters below one of the city's arteries, Kannana Dori ("Ring Road 7"). By the beginning of the next century, the planners expect to have completed a 30-kilometer extension that will drain directly into Tokyo Bay.

Numerous Benefits
From the 1960s through the 1970s, large-scale subterranean shopping districts began cropping up in all sorts of places in Japan: at center-city terminals; in bustling neighborhoods; beneath roads and buildings; and around concourses and thoroughfares in subway stations and other public spaces. These underground shopping streets caught on because they eased traffic congestion, encouraged commercial expansion, and were convenient for the public, offering benefits that included shelter from rain.

During the bubble years of the late 1980s, developers again directed their attention underground, but for a different reason: Land prices were skyrocketing and the supply of available land was inadequate. General contractors came up with a flurry of underground construction plans, some reminiscent of science-fiction movies. But when the economic bubble burst, these fanciful schemes collapsed along with it.

But now interest in underground construction is growing again. This time it has been sparked by a renewed recognition of the inherent advantages of underground spaces. The Kobe earthquake of January 1995 served as a reminder that subterranean facilities are less vulnerable to natural disasters: The underground shopping district at Kobe's Sannomiya station escaped the major damage seen throughout the surrounding area. People are also remembering another merit of underground spaces: They conserve energy. Although construction costs are typically twice those for above-ground projects, climate-control costs are dramatically lower. According to some experts, subterranean construction has an overall advantage when things like safety and reduced impact on the above-ground environment are taken into account.

The Agency of Industrial Science and Technology within the Ministry of International Trade and Industry has embarked on a research-and-development project aimed at increasing utilization of subterranean spaces. Last May in Sagamihara, Kanagawa Prefecture, the agency completed construction of a dome-shaped underground facility 70 meters below ground level, 20 meters in diameter, and 12.5 meters in height, where it plans to carry out a variety of experiments. Among other things, the agency seeks to develop technologies for creating comfortable subterranean environments, and for preserving safety in times of disaster.

It seems that the motivation for subterranean development in Japan has changed. Rather than being pushed underground by the disadvantages of above-ground spaces, development is being pulled underground by the unique merits of the subterranean environment.

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