Japanese $20 Billion Airport Island
Japanese $20 Billion Airport Island
Three miles off the coast of Japan sits a gargantuan monument to human ingenuity and ambition.
The size of two and a half thousand football fields, it incorporates the world’s longest building and took an estimated 10,000 workers ten million man-hours to build.
Kansai airport typically processes 920 flights and more than 30 million passengers a year. Not bad, when you consider it’s already sinking below the choppy waters of the bay of Osaka.
How did engineers pull it off in just four years?
And how long can it put up with the looming threat of rising sea levels?
Join us today as we check in to investigate how Japan built the world’s largest floating airport.
During the 1980s the city of Osaka and its surrounding area was undergoing a crisis. Rival city Tokyo was attracting tourism and a bumper slice of the national export business, thanks in no small part to its shiny new Narita international airport.
Osaka’s Itami airport, by contrast, was aging badly and hemmed in by densely populated suburbs, making any expansion impossible.
In Japan, where something like 80 percent of all land is mountainous in character, flat places to build things like airports are at a premium and are almost always densely populated.
Even if the Japanese government was in the mood to snatch land off landowners for the greater good, its experience building Narita airport – where bitter protests against the Tokyo project led to thousands of arrests and seven deaths – make this a non-starter So for the city of Osaka to develop new air capacity it had to start thinking outside the box.
Japanese city planners had flirted with artificial islands in the past, to make up for limited land availability during the economic boom years of the 60s.
But to build an island on the scale needed for a major international airport would require a different magnitude of ambition and ingenuity together.
Moreover, the Bay of Osaka is notorious as a center for deadly seismic activity. It’s also prone to unpredictable and destructive typhoons, like one famous 1934 storm that caused water in the bay to rise fully 10ftkilling 3,000 locals.
At least the project wouldn’t have to deal with local dissent – apart from disruption to fishing lanes, wisely settled early with a binding payout to the local fishing community.
A crack team led by starchitect Renzo Piano– famous for designing the Pompidou Centre in Paris and The Shard in London – set to work directly.
The site selected, three miles out to sea, had a depth of around 60 feet below which lurked a layer of soft alluvial clay.
This material is familiar to marine engineers, but at this distance from shore a significantly trickier base layer of diluvial clay, around1,000ftthick, would need to be tamed in order to support the entire airport.
Using core sampling techniques and educated guesswork, civil engineers estimated the airport island might sink into this goopy mess anywhere between 19 and 25 feet before ultimately settling.
In the interests of cost-cutting, project leaders crossed their fingers and hoped for only 19 feet of sinkage.
Then, gingerly, they proceeded with the build. In order to strengthen those soft clay layers, around a million pipes were drilled deep into the sea bed.
These were then filled with sand, and the pipes removed, leaving a million or so sand columns to absorb the moisture from the surrounding sponge-like clay.
Then it would hopefully settle and support the weight of the airport. The clay was squeezed still further by a five-foot-deep layer of sand on top of the columns.
The next phase involved constructing the seawall, the first leg of which was seven miles long.
Gigantic rocks were dropped from boats and maneuvered into place by daredevil divers – at least one of whom was forced to have a leg amputated after a freak tide moved one of those vast boulders.
Eventually, the sea walls rose proudly 75 feet off the seafloor. The wall was then coated on its south and west-facing flanks with 48,000 concert four-pointed blocks, designed to dissipate and deflect the awesome power of the incoming currents.
Two and a half years since the project started, by 1989 it was time to stuff the gap in the middle of the wall with enough soil to fill it.
No easy task.
A fleet of 80 ships took three years transporting material excavated by various means. Some soil was dredged from the bottom of the bay, while separate massive teams excavated earth from three local mountains on the land.
Project leaders even imported some of the precious matter from China and Korea. Ships carrying the precious spoil were methodically choreographed to precise GPS locations above the seafloor before dumping.
Three different sizes of rock and gravel were used in the final mix, a measure that experts believed should help the ground stay solid in the highly probable event of a future earthquake.
Eventually, slowly but surely, the island that would house the first phase of the airport emerged from the sea.
In the meantime, a one-of-a-kind record-breaking bridge connecting the airport to the mainland was gradually taking shape. Gigantic floating cranes arrived and started lowering the first of 29 enormous pilings into the sea bed.
Two years later, the colossal 4,000 tonnes,500-feet bridge modules were lifted into place. The bridge along – with a highway on the top deck and a railway down below – is two miles long, and costs over a billion dollars.
The bridge design incorporates clever flexible joints, a smart move by engineers concerned about the future impact typhoon winds might have over the lifetime of the structure.
Meanwhile, on the island, nature’s presence was already making itself felt.
In the spring of 1990, it was reported that the island was sinking.
This was already expected, of course. But the rate and extent of sinking alarmed everybody involved. By March of that year, the island should have sunk a mere 19 feet.
But it was already down 27 feet and was descending by at least a couple of inches every month. Another 11 1/2 feet of soil was promptly dumped on top, at an eye-watering cost of US$150 million.
An attempt was made to compact the soil quickly using the frankly cartoonish method of repeatedly dropping a 20-tonne weight onto the runway from 100 feet up in the air.
The biggest problem wasn’t the subsidence itself, but the uneven manner in which it was happening. Different parts of the island were sinking at different rates, and the planned terminal building would inevitably split and breakin months if this was left unchecked.
Part of the solution involved adapting RenzoPiano’s design so the foundations could be beefed up with an eight-foot layer of crushed iron ore, to help the light structure at least collapse evenly and at the same rate as the island itself.
The most ingenious workaround involved however the installation of some 900 jacks into the foundations.
These jacks – atop which rested the terminal superstructure, all 3 million tonnes of it – incorporate sensors to keep engineers abreast of which parts are sinking, and by how much.
The relevant jacks could then be adjusted to keep those gigantic 30 steel trusses and 250 ribs that form this 1.7km-long leviathan on a roughly even keel.
The terminal building, rendered in the shape of a segment from a giant toroid, is covered in some 5,000 panels of glass, each set within a rubber frame so as not to shatter in high winds.
On the roof, there are 90,000 stainless steel tiles, painstakingly installed by hand and tested to bear the stresses and strains of a major earthquake or typhoon.
As you can imagine, even during construction the project had to put up with some fairly intense sea breezes.
The huge internal space is elegant spread over four stories. It can be accessed from the mainline by car, train, or hydrofoil and is studded with 41 gates, each no more than 90 seconds travel from the terminal concourse proper.
That 100-foot high ceiling is designed with a curve in the top to mimic patterns of air circulation and thus support fresh airflow.
These colorful mobiles bob about in the invisible whorls and eddies to give you an idea of how breezy it is up there.
Those jacks underneath the structure certainly have their work cut out.
Designed to move the columns above up to 15 inches at a time, they also accommodate iron plates which engineers periodically slide into the voids to keep the structure above from collapsing.
It's a bit like wedging a book under the wobbly leg of a table.
Beneath the terminal, this elastic quality is still evident in service staircases that have grown by one or even two steps over time as the ground has sunk or these quirky doors with uncommonly high frames.
Interior remodeling like this was the least of engineer’s worries when a deadly 7.2 magnitude earthquake rocked the city of Kobe on Jan 17, 1995, killing 5,000 people, injuring 25,000, and leaving 300,000 Japanese homeless.
Yet despite being only 18 miles from the epicenter, Kansai airport remained miraculously unscathed, thanks to the variable-sized rocks in the island foundation and ingenious deployment of sliding and rotating joints throughout the structure.
In fact, not only was the airport spared, but it was capable of a leap into action immediately as a staging area for emergency crews and the distribution of food and supplies to the stricken region.
Even those glorious glass tiles were left intact. Engineers could justly give themselves a pat on the back for that day’s word, and again three years later when a powerful typhoon saw 130mph winds whip across the Bay of Osaka.
Still, despite minor damage to the roof, the airport was able to open that very same evening.
In 2007 the airport – facing big rises in passenger numbers, and buckling under hefty construction debts which meant owners were forking out some $500million a year in interest payments alone on the airport’s total $20bncost – opened its second runway.
This is aimed at the low-cost carrier market and is graced with a substantially cheaper, simpler one-story terminal building.
Passenger growth increased steadily with a brief wobble after 2018’s typhoon Jebi caused the airport to be temporarily flooded, and its bridge was struck and by a tanker vessel.
That is until the covid pandemic saw a brutal76% year-on-year collapse in passenger numbers from 2019 to 2020.
And despite regular upgrades to the sea wall, some academics – in particular Gholamreza Mesri, professor at the University of Illinois at Urbana-Champaign – predict the islands might be in danger of another overwhelming typhoon as soon as the year 2023.
Still, just last month VINCI Airport groups announced an expensive modernization program to upgrade Renzo Piano’s groundbreaking terminal building.
According to a breathless press release, the new look will “… offer visitors immersion in a welcoming and experiential space.” ‘Immersion’ probably isn’t the word we'd have chosen, but anyway. Japanese $20 Billion Airport Island
