Kansai International Airport, the third-largest in Japan, is sinking faster than expected. Why did Japan opt for constructing an artificial island for an airport that could potentially sink in the future?
DALLAS — Let's delve into the remarkable engineering feat of Japan's Kansai International Airport (KIX), situated near Osaka Bay, which stands as the world's most expensive civil engineering project to date.
Despite grappling with various environmental challenges, Japan has emerged as a vital hub in the Asia-Pacific (APAC) region. Tokyo, with a population of 14 million, holds the distinction of being the most densely populated metropolitan area globally.
Consequently, the country has made substantial investments, amounting to billions of dollars, in its infrastructure. Japan now boasts nearly 100 airports operated by the central and local governments.
The primary airports in Japan in terms of passenger traffic include Haneda International Airport (HND), followed by Narita International Airport (NRT), Kansai International Airport (KIX), and Fukoma International Airport (FUK). Collectively, these four airports accommodate nearly 200 million passengers each year.
Now, the question arises: why did Japan opt for constructing an artificial island for an airport that could potentially sink in the future? To unravel this query, we need to revisit the period when the Japanese government and its engineers initially conceived the idea of building a floating airport.
In the 1960s, Japan's Kansai province faced a decline in business compared to Tokyo, prompting planners to propose a new airport project near Kobe and Osaka. The existing Itami Airport (ITM) was unable to accommodate further expansion due to congestion in its vicinity. Additionally, the expected costs of expanding Itami Airport were deemed significantly higher than the construction of a new airport, unless the issue of KIX's rapid sinking was addressed.
Amidst protests against the Narita Airport (NRT) due to the expropriation of rural land, planners put forth the idea of constructing an offshore airport. The initial proposal suggested building the airport near the Kobe region; however, city officials rejected this plan, leading to a shift in construction to the southern part of Osaka Bay. Thanks to its unique location, the airport has the advantage of operating 24 hours a day.
With the necessary approvals from authorities, the project was estimated to cost the government approximately US$1 billion. The construction of a new airport was part of a broader effort to revitalize Osaka, which had been ceding financial and cultural prominence to Japan's capital city for over a century.
Japan initially announced plans to construct a floating airport. However, similar to other so-called "floating airports," these structures are built on artificial islands rather than directly on water. To prevent sinking, water is pumped out of the sand foundation.
Many engineers believe that a floating airport should be constructed like a raised structure rather than a traditional barge-like design. This is because barge-like structures are not suitable for oceanfront locations due to tidal and wave action. To eliminate vertical movement on the airstrip, a raised structure with numerous vertical floats must be employed to take advantage of the buoyancy effect.
Vertical movement would pose significant risks for commercial planes during takeoff and landing, and it would also lead to increased maintenance costs for the airstrip structure. It is surprising that many designers overlook or fail to address these critical issues in their proposed designs.
The proposed plan involved the creation of an artificial island measuring four kilometers (two and a half miles) in length and two and a half kilometers (one and a half miles) in width. Engineers constructed an airport on this island, utilizing millions of solidified sand drains to ensure its resilience against earthquakes and typhoons.
Kansai International Airport is situated within the renowned Pacific Rim of Fire, an area known for experiencing a significant number of the world's costliest disasters. Japan had previously constructed numerous structures along the shoreline, but this project differed as it was set to be located three miles offshore in water that was 60 feet deep. This presented unique challenges, requiring two distinct seabed layers to support the facility.
To create a firm and level surface, approximately 180 million cubic meters of rock and soil were added to the sand layer, sourced from three nearby mountains. Additionally, a seawall consisting of 48 thousand concrete tetrapods was constructed to protect the foundation. The seawall's perimeter was reinforced using 69 large steel chambers. Without this protective barrier, the airport would be vulnerable to flooding from Osaka Bay.
In 1991, the construction of the terminal began. To counteract the sinking of the island, adjustable columns were installed to support the terminal building. These columns can be extended by inserting dense metal plates at their bases.
While government officials considered shortening the length of the terminal to reduce costs, architect Renzo Piano, the Italian designer of KIX, recommended maintaining the original planned length. He also proposed constructing a low-profile terminal to ensure that air traffic controllers in the ATC tower always have a clear view of the airplanes on the runways.
Back in 1990, the airport island was connected to the mainland town of Rinku through the construction of the Sky Gate Bridge R, costing approximately US$1 billion. This remarkable bridge, known as the "Sky Gate Bridge R," spans a total length of 3750 meters.
Interestingly, the bridge surpasses the length of Runway A at KIX, which measures 3500 meters and falls short of the length of Runway B, which spans 4000 meters. However, when the average length of both runways is considered, it aligns with the length of the KIX Access Bridge—an intriguing coincidence indeed.
The Sky Gate Bridge R is a double-decked bridge, accommodating six lanes of traffic on its upper roadways, while beneath them, two rail lines are present. It is commonly referred to as the Kansai International Airport Access Bridge, serving as a vital connection to the airport.
After 20 years of planning, three years of construction, and a staggering investment of US$15 billion, the construction of Kansai International Airport (KIX) was finally completed. The airport opened its doors to the public on September 4, 1994, serving the bustling regions of Osaka, Kobe, and Kyoto as a hub for international air travel. Notably, it serves as a major hub for All Nippon Airways (NH), Japan Airlines (JL), and Nippon Cargo Airlines (KZ).
Despite its significance, the 511-hectare island airport has accumulated substantial debt, with an annual loss of US$560 million in interest payments. The airport faces the ongoing challenge of staying competitive against Incheon International Airport (ICN) and Hong Kong International Airport (HKG) while maintaining its position as a gateway to Asia.
To offset the immense construction costs, the government has increased rent and landing fees. At one point, KIX had the highest landing fees among all airports worldwide. For instance, the airport charged approximately US$7,500 for a Boeing 747 to land, compared to US$2,500 at New York's JFK Airport (JFK). Some have even suggested that a cup of coffee would need to be priced at over ten dollars to cover the airport's expenses.
In response to the growing demands of business owners in Osaka, the administration was urged to assume a greater share of the construction costs for KIX. This initiative aimed to maintain the airport's attractiveness to both passengers and airlines, while also reducing the overall cost of conducting business and potentially boosting profits.
As tourism in Japan experiences exponential growth, KIX has witnessed a rise in passenger traffic. The Japanese government actively promoted KIX as a viable alternative airport for international passengers traveling to Greater Tokyo, offering flights connecting HND and KIX as an alternative to NRT.
We pause here to mention that there is a persistent misconception that "floating" airports are more expensive to build compared to land-based airports. In reality, land-based airports in bustling urban areas often have construction costs that are approximately half of what it would cost to build a floating airport.
However, as one of our avid readers pointed out, the overall cost of a land-based airport increases significantly due to expenses associated with acquiring the land and obtaining the necessary legal permissions. As a result, the total cost of a land-based airport can be equal to or even exceed that of an airport built on an artificial island.
In 2003, the increasing number of passengers and the limitations of the existing runways, particularly during peak times and due to cargo flights, necessitated the expansion of KIX. Engineers were confident that the issue of sinking had been stabilized, allowing them to proceed with phase two of the project. This phase involved the construction of a new parallel runway and a second terminal.
To create the second island, engineers followed a similar process as they did with the first one. However, this time they adjusted their measurements, taking into consideration the anticipated sinking of the island until it reached the allowable limit. The construction of the 4,000-meter-long second runway was completed, and it became operational on August 2, 2007. The implementation of phase two incurred an additional cost of approximately US$8 billion for the airport authority.
"The renovated airport will support Japan’s economic development in the post-COVID-19 period."
VINCI Airports
Japan announced in 2021 the extension and renovation of the airport. Once this project is completed, KIX will have the capacity to accommodate nearly 40 million international passengers each year.
This new undertaking is considered to be the largest airport renovation project in the region over the past 50 years. The aim is to finish the renovations in time for Expo 2025 Osaka in Kansai, an event of great significance.
The primary terminal at Kansai International Airport, Terminal 1, is a four-story building with a total floor area of 296,043 square meters (3,186,580 sq ft). It holds the distinction of being the world's longest airport terminal at 1700 meters in length, although Beijing's Daxing Airport now holds the title of the world's largest terminal.
The design of Terminal 1 includes a unique airfoil-shaped ceiling, which serves to enhance air circulation throughout the facility. Large air conditioning ducts blow air upwards on one side of the terminal, distributing it across the curved roof, and then guiding it through vents on the other side.
Terminal 2 is specifically dedicated to Low-Cost Carriers (LCCs), such as Peach (MM), Spring Airlines (9C), and Jeju Air (7C), although some LCCs also operate from Terminal 1. Terminal 2 is a single-story structure with corridors leading directly to the aircraft, which do not have air conditioning.
Additionally, there are no jet bridges in Terminal 2, instead, it has one boarding gate for domestic departures and another for international departures. Instead, buses are available to facilitate passenger movement between them.
Itami Airport, since 1994, has exclusively served domestic flights, with a few exceptions including charter flights and VIP flights. To encourage the use of Kansai International Airport, the government imposed restrictions on Itami, including permitting only two-engine planes since 2006.
In 2012, the authorities of Kansai and Itami airports were merged, resulting in various improvements in joint operations. Examples of these enhancements include bus connections between the two airports and a reduction in landing fees at KIX.
In 2016, Kansai Airports, a private Japanese consortium, obtained a 45-year operational contract from the government and took over the operations of both Kansai and Itami airports.
As of 2019, Kansai Airport ranked as the third busiest airport in Japan and the 30th busiest in Asia. That year it recorded the following passenger and cargo traffic data (Please note that these figures are sourced from the Kansai Airport website):
For comparison, Tokyo Narita Airport reported handling 33.4 million passengers and 2.2 million tonnes of cargo in 2018, according to government data.
In 2019, Kansai Airport saw a total of 206,776 flight movements and hosted operations by 86 different airlines, serving over 100 destinations. However, due to the impact of the COVID-19 pandemic, passenger traffic experienced a significant decline in 2020-2021, while freight flights remained relatively stable.
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In September 2018, Typhoon Jebi struck Japan, becoming the most powerful storm to hit the country in the last 25 years. The storm made landfall in southwestern Japan with winds reaching up to 130 mph, causing significant damage and disruption. The storm resulted in severe flooding and inflicted substantial damage on KIX.
The impact of Typhoon Jebi led to the closure of KIX due to the extensive flooding caused by the storm. The airport, located on a man-made island in Osaka Bay, experienced significant damage as a result of the typhoon's force. The storm disrupted transportation networks, damaged the bridge connecting the airport to the mainland, and caused power outages affecting over a million homes, as reported by The New York Times.
The engineers involved in the construction of KIX underestimated the rate and depth at which the airport island would sink during the initial phase of construction, despite the inevitability of the sinking problem.
At the time of its opening, KIX had already sunk 38 feet (11.5 meters). However, during the early stages of construction, the engineers had estimated that the first island would sink between 19 and 25 feet (5.7-7.6 meters). Unfortunately, they ultimately considered lower values, specifically 19 feet of sinking, which proved to be a costly mistake.
Initially, it was estimated that the airport island would continue to sink for 50 years until it stabilized at an elevation of 13 feet (around 4 meters) above sea level, which is the minimum height required to prevent severe flooding.
However, by the year 2000, the first island had sunk at a faster rate and was only 13 feet above sea level. Subsequently, engineers recalculated the sinking rate and conducted surface samples, leading to new predictions. It is now projected that the airport will sink an additional 13 feet and reach sea level by 2056.
To mitigate further sinkage, over 150 million US dollars have been spent on strengthening and raising the seawall surrounding the airport. However, raising the seawall alone is not a comprehensive solution, and engineers have implemented temporary measures as well.
In 1999, issues became more apparent as the first island had already sunk 27 feet (8.2 meters), exceeding the original estimates by nine feet. Engineers took action to slow down the sinking process by excavating the ground beneath the main terminal and installing iron plates beneath hydraulic jacks and 900-column foundations. The foundation was raised in stages, which helped to reduce the rate of sinkage.
While the immediate sinking of the airport in Osaka Bay is not an imminent concern, the sinking issue is far from resolved. The hydraulic jacks supporting the airport need to be adjusted every two years, and the costs associated with maintenance and repairs have significantly increased.
If the airport is not adequately raised, it could become unbalanced, leading to further sinking and potentially requiring its evacuation and permanent closure.
The sinking problem is particularly severe in the central area of the island, where vital airport facilities are located. Five out of the 17 monitoring points at KIX, including the main terminal and a section of the 3,850-yard runway, have already met or exceeded their projected sinking levels for 50 years.
Although administrators claim to have learned enough from these experiences to avoid similar sinking problems when constructing the new runway, many citizens of Osaka, who are responsible for covering the cost overruns, remain skeptical.
The sinking of Kansai International is not an immediate threat, but considering Japan's unpredictable natural calamities and the airport's existing sinking issues, further sinking cannot be ruled out.
The project has generated mixed reviews, with some considering KIX to be the greatest engineering achievement in the world, while others view it as a major engineering disaster in modern history.
The question of whether KIX will survive and remain operational until 2056, as anticipated by the engineers, or sink below sea level is a matter that only time can answer. However, Japan's floating airport will continue to serve as a crucial facility for handling passenger overflow from its busiest airports, HND and NRT.
No matter what lies ahead for this remarkable structure, the fact that it was constructed against numerous challenging odds is a testament to its miraculous nature.
We are interested in hearing your perspective on whether you consider KIX to be an engineering marvel or a failure in civil construction. Please share your thoughts in the comments section of our social media channels.
Feature Image: Kansai Airports
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