Stormwater Management and Road Tunnel

Year:2007

Duration:4 years

Cost:£358m (£456m today)

Country: Kuala Lumpur, Malaysia

What did this project achieve?

Devise a tunnel that cars can drive along but also work as a drain to cope with floods

The Stormwater Management and Road Tunnel (SMART tunnel) in Kuala Lumpur, Malaysia is a tunnel that doubles up as roadway for vehicles and a channel to get rid of storm water.

Flash flooding has been a problem in Kuala Lumpur for many years. When a drainage tunnel was suggested to stop the city's rivers flooding during heavy rains, local authorities realised it could also help reduce traffic congestion.

The resulting 9.7km tunnel has 2 functions: to reduce flash flooding in Kuala Lumpur and cut traffic jams at rush hour.

The storm function of the SMART tunnel sees flood water caused by heavy rain diverted into a bypass tunnel under the motorway tunnel.

If the rains continue and flooding gets worse the motorway tunnel is closed to vehicles - allowing water to flow through both the traffic and bypass tunnels.

The structure is the longest multi-purpose tunnel in the world and the longest stormwater drainage tunnel in South East Asia.

The SMART tunnel won the UN Habitat Scroll of Honour award for its innovative and unique management of storm water and peak hour traffic in 2011.

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.

"​‌

We used state of the art technology and unique safety features to build this tunnel.

Mohd Fuad Kamal Ariffin

SMART general manager, 2007

Fascinating facts

Closing the tunnel to traffic only happens during major storms. Floodgates seal it off at each end and water from Kuala Lumpur's rivers is pumped through to stop them breaking their banks.

Over 200 CCTV cameras linked to a central control room make sure there are no vehicles left in the tunnel before it fills with water.

The motorway tunnel is cleaned with high-pressure water jets after flooding. It re-opens within 48 hours.

People who made it happen

  • Client: Malaysian government
  • Structural engineers: MMC Corporation Berhad
  • Consulting engineers: Mott MacDonald UK

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