Water leakage
White patches can be seen on various part of the tunnel wall. The size of the patches varies and they are lighter in some areas than in others. What is the cause of these?
From time to time, water seeps in through the tunnel wall. This is mainly due to the connection between two tunnel rings. The white marks are created when the leaked water dries on the surface and leaves behind remnants of calcium on the heat-resistant lining of the tunnel. You can often see a white discharge on new brickwork, for instance when new houses are being built. This is known as ‘efflorescence’ and goes away on its own. The white marks on the tunnel are actually the same phenomenon.
Does the Westerscheldetunnel leak?
Yes, it does. All tunnels leak. This happens because a tunnel is made up of separate sections. Water mainly leaks around the joints between the tunnel segments. These segments have a rubber seal. When it is warm, the tunnel structure expands. It contracts when temperatures fall. This means that tunnels leak more during Winter months than during the Summer.
The leakage water is collected beneath the carriageway in the lowest part of the tunnel. This is called the sole of the tunnel. The water flows through pipes from the sole of the tunnel to a total of four pump pits. This water is then pumped back into the Westerschelde estuary from the pump pits.
The Westerscheldetunnel is designed to allow for a maximum of 22 m3 of leakage water every twenty-four hours. This is 22,000 litres and the pump capacity has been calculated for this volume. In practice, the tunnel leaks far less. In 2003 (the year of its opening), the Oostbuis leaked approximately 3 m3 every twenty-four hours and the Westbuis leaked 3.5 m3 during the same period. The volume of leakage water is falling each year. In 2012, the Oostbuis leaked 2.2 m3 and the Westbuis leaked 2.8 m3 of water every twenty-four hours.
