Groundwater on Kansai International Airport Island – Before Cutoff Wall Construction

The rise in groundwater levels was related to the structure of the island. KIX is surrounded by an environmentally-friendly seawall made of stones. The interior of this seawall is filled with material made by crushing mountain rock and soil which contains stones around 30 cm in size. It is very easy for water to pass through this fill material.

Consequently, when the sea level rose, seawater flowed through the seawall and mixed with the island's groundwater, causing the groundwater level to rise. When the sea level dropped, the groundwater also lowered in turn. Monitoring showed that groundwater levels rose and fell more or less in tandem with changes in sea level.

Structure of the KIX Island (Cross-section)

Structure of the KIX Island

Changes in Groundwater Level under KIX

In addition, abnormally high sea levels have occurred for no clear reason in recent years. These have happened repeatedly nationwide, and there have been a greater number of days with unusually high tides.

Very high tides have caused problems on the airport island, for example, poor drainage of low-lying grassy areas, and basement water leakage in certain facilities.

Countermeasures against Rising Groundwater Levels – Underground Wall Construction

As a radical solution to such problems, a underground wall (a special kind of subterranean wall) was constructed in order to prevent seawater from mixing with groundwater, and thus stop rising groundwater levels.

Construction of the underground wall involved digging down around 30 m to the holocene clay layer, and building a series of water-resistant pillars made from a mixture of cement, earth, and sand.

Installation of the Underground Wall

Construction of the Underground Wall

Construction in Progress

Construction in Progress

Installation Site of the Underground Wall, Enlarged Drawing

Groundwater Levels after Underground Wall Construction

Construction of the Underground Wall surrounding the entire airport island was completed in 2006. The wall has successfully prevented rises in groundwater levels due to abnormally high sea levels, and high tides caused by typhoons. The Underground Wall will effectively provide full protection against future rises in sea level due to long-term global warming and ground settlement, and will ensure that these phenomena do not affect the operational capabilities of the airport.

Changes in Groundwater Level under KIX after Underground Wall Construction