AN AIRPORT touted as the world’s most unique is sinking into the sea at an alarming rate.

The Kansai International Airport serves Japan’s second largest metropolitan area, Osaka, and has sunk more than 38ft since it opened 30 years ago.

Kansai is sinking into the sea at an alarming rateCredit: Getty

The busy airport continues to be used every dayCredit: Getty

The Sayonara bridge which leads out to the airport cost £786,000Credit: Shutterstock

The enormous £15billion airport occupies two artificial islands in Osaka Bay and serves as a hub for Asian airlines including All Nippon Airways, Japan Airlines, and Nippon Cargo Airlines.

It is also sinking – quickly – and moving further and further away from the city.

Engineers predicted Kansai’s islands would evenly settle over a 50-year period before stabilising at 13ft above sea level – the minimum elevation needed to prevent flooding in case of a breach in the encircling seawall.

The threshold was reached within just six years and £117million was spent raising the seawall, which some would say was a futile attempt to prevent the inevitable.

A number of engineers have predicted that sections of the two artificial islands may sink another 13ft – to sea level – by 2056.

Yukako Handa, a representative of Kansai Airports was quoted by Smithsonian Mag in 2018 as saying: “When the Kansai airport was constructed, the amount of soil to reclaim the land was determined based on necessary ground level and subsidence estimation over 50 years after the construction.”

The reclaimed land was like a wet sponge and needed to be transformed into a dry and dense foundation before it could support the weight of airport buildings.

Construction crews laid sand five feet deep atop the clay seabed then installed 2.2 million vertical pipes, each nearly 16 inches in diameter.

The pipes were then pounded into the clay and filled with sand, with soil used to create a stiffer floor.

Workers excavated below the passenger terminal, inserted plates beneath the hydraulic jacks, and raised the columns to try and save the airport from the sea.

And yet it continues to sink – at different rates, too, because the airport isn’t actually even.

Kansai is the world’s first airport to be built on water and attracts an average of 20 million jetsetters every year.

Isolated and without shelter or protection, it has been repeatedly struck by extreme weather conditions.

The worst came in 2018, when the deadly typhoon Typhoon Jebi struck, wreaking havoc across Japan and causing the airport to close temporarily.

Thousands of terrified passengers became stranded as the storm flooded the building and shook the infrastructure.

The typhoon then grabbed hold of a tanker and repeatedly slammed it against a bridge, leaving millions of pounds worth of damage.

Kansai recently announced it will be carrying out an earthquake and tsunami drill so its staff are prepared for weather-related emergency situations.

Engineers expect Kansai will sink to sea level by 2056Credit: Shutterstock

It was initially thought the airport would settle over a 50-year periodCredit: Shutterstock