Stormwater Management and Road Tunnel

Difference the tunnel has made

Since the tunnel opened flash flooding in Kuala Lumpur has been reduced – particularly during the heavy rains which generally fall 2 or 3 times a year.

The tunnel has also helped traffic congestion. For example, travel time between the Jalan Istana Interchange and Kampung Pandan in eastern Kula Lumpur was about 10-15 minutes before the tunnel. It's now around 4 minutes.

How the work was done

The SMART tunnel begins at Kampung Berembang lake near the river Klang at the town of Ampang. It runs to Taman Desa lake near Kerayong river close to Salak South, a town at the southern tip of Kuala Lumpur.

The tunnel diverts water from a holding pond on the river Klang to a reservoir on the Kerayong river.

Engineers working on the project had to follow the route of existing highways to avoid charges for digging under private property.

The project team had to tunnel underground - rather than use cut and cover methods - to reduce disruption on the surface. This meant using what were 2 of the largest tunnel boring machines (TBMs) in the world at the time.

The circular TBMs were 13m wide and 71m long – longer than a 747 jumbo jet and weighing the same as 12 of them.

As the 2 TBMs were moving only 20m below the surface engineers had to monitor drilling carefully to make sure buildings above ground stayed stable.

Challenges included the make-up of the ground – limestone covered with a layer of sediment. The limestone had been dissolved in places by water and crumbled easily. This made the going unpredictable.

Earth excavated by the TBMs was pumped to the surface in the form of slurry – a semi-liquid mixture – for removal by lorry.