When Japan’s Kansai International Airport (KIX) opened in 1994, it was considered an engineering marvel. It is one of the world’s floating airports and cost around $20 billion to build.
30 years later, it is still an important hub in Japan.
In 2022, Statista named KIX the third busiest airport in the country, after Narita International Airport (NRT) and Tokyo Haneda Airport (HND).
The airport serves as a hub for major airlines including All Nippon Airways, Japan Airlines, Nippon Cargo Airlines and even Japan’s low-cost carrier Peach.
But now experts sound the alarm:
– The KIX airport could be completely underwater by 2056, writes Aerotime.
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Osaka Bay. Far down there is the floating airport Kansai International Airport – it is sinking faster than the experts expected. Photo: Yujun3 / Shutterstock / NTB
Built as a replacement
Kansai Airport was built to relieve overcrowding at Osaka’s first airport: Itami Airport (ITM).
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Kansai’s original location was envisioned near Japan’s Kobe region, but city officials and local residents protested the plan.
Instead, the authorities therefore decided to build the new airport in a unique location – in the middle of the sea, where operations can take place 24 hours a day without disturbing the local population.
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To build an airport in the middle of the sea, engineers drained millions of liters of water from the 20-meter-deep soft clay that lies beneath the airport’s current location, before building a seaward wall.
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The reclaimed land resembled a wet sponge, but was transformed into a dry and dense foundation to support the weight of the airport buildings.
Construction crews placed a five-foot-thick layer of sand on top of the clay bed and installed 2.2 million vertical pipes, each nearly 16 inches in diameter. These pipes were then pounded into the clay and filled with sand and soil to create a more stable base.
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Kansai International Airport, Osaka, Japan Photo: Flayd Isoji / Shutterstock / NTB
Seven years of construction time
Construction of KIX Airport began in 1987 and took seven years to complete.
Throughout its 30 years, the floating airport has withstood a major earthquake in 1995. The Great Hanshin earthquake which reached a magnitude of 7.2 and claimed more than 6,000 lives.
In 1998, the airport also survived typhoon Stella, which triggered over 70 landslides.
It was known that the airport would sink because of the ground. But it is declining faster than expected. In 1990, it was calculated that the “mushroom” foundation would cause the airport to sink 5.7 meters.
It is much more dramatic:
In a 2018 Smithsonian Magazine interview, Yukako Handa, a representative of Kansai Airports was quoted by Aero Time as saying:
“When Kansai Airport was built, the amount of soil to reclaim the land was determined based on the required ground level and subsidence estimate over 50 years after construction.
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By 2018, the airport had sunk 38 feet (11.5 meters) since it was built, 25% more than experts expected.”
But the Japanese are positive and believe the outlook is still positive. The airport has continued to expand.
In December 2023, a new international departure area was opened. Future extensions are to be completed by 2025.
