Kansai International Airport is Japan’s second most important international airport, located on an artificial island in the middle of Osaka Bay, 38 km southwest of Ōsaka Station. The airport was opened in 1994 to relieve overcrowding at Osaka International Airport, which is located in the densely-populated suburbs of Itami and Toyonaka surrounded by buildings and therefore could not be expanded. A man-made island, 4 km long and 2.5 km wide, was proposed.
Construction started in 1987. A sea wall was erected made of rock and 48,000 concrete blocks. Three mountains were excavated for 21,000,000 cubic meter of landfill. 10,000 workers and 10 million work hours over three years, using eighty ships, were needed to complete the 30-metre layer of earth over the sea floor and inside the sea wall. A three kilometer bridge connects the island to the mainland.
The total cost of Kansai Airport is estimated to be $20 billion. This includes land reclamation, two runways, terminal and facilities. Most additional costs were initially due to the island sinking, expected due to the soft soils of Osaka Bay. After construction the rate of sinking was considered so severe that the airport was widely criticized as a geotechnical engineering disaster. Despite the early misfortunes, the Kansai International Airport is a great engineering achievement. In 2001, the airport was named one of ten structures given the “Civil Engineering Monument of the Millennium” award by the American Society of Civil Engineers.
Much of what was learned from the construction of the Kansai International Airport went into the successful construction of three more airports on artificial islands – New Kitakyushu Airport, Kobe Airport, and Chūbu Centrair International Airport, all in Japan.