Kansai International Airport
A man-made island, 4 km (2.5 mi) long and 2.5 km (1.6 mi) wide, was proposed. Engineers needed to overcome the extremely high risks of earthquakes and typhoons (with storm surges of up to 3 m (10 ft)).
Construction started in 1987. The sea wall was finished in 1989 (made of rock and 48,000 tetrahedral concrete blocks). Three mountains were excavated for 21,000,000 m3 (27,000,000 cu yd) of landfill. 10,000 workers and 10 million work hours over three years, using eighty ships, were needed to complete the 30-metre (98 ft) layer of earth over the sea floor and inside the sea wall. In 1990, a three kilometer bridge was completed to connect the island to the mainland at Rinku Town, at a cost of $1 billion. Completion of the artificial island increased the area of Osaka Prefecture just enough to move it past Kagawa Prefecture in size (leaving Kagawa as the smallest by area in Japan).
On 17 January 1995, Japan was struck by the Kobe earthquake, whose epicenter was about 20 km (12 mi) away from KIX and killed 6,434 people on Japan’s main island of Honshū. Due to its earthquake engineering, the airport emerged unscathed, mostly due to the use of sliding joints. Even the glass in the windows remained intact. Later, in 1998, the airport survived a typhoon with wind speeds of up to 200 km/h (120 mph).
The total cost of Kansai Airport so far is $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. The sink rate has since fallen from 50 cm (20 in) during 1994 to 7 cm (2.8 in) in 2008.