Inside KL’s SMART Tunnel: The hidden work behind its flood-fighting operation

KUALA LUMPUR, Oct 29 — The SMART Tunnel in Kuala Lumpur remains a hidden marvel to most motorists, with its flood mitigation capabilities rarely seen. Under the city's surface, this 9.7km-long infrastructure plays a crucial role in diverting excess water during heavy rain. Constructed using a 13.2-metre-diameter Slurry Mix-Shield tunnel-boring machine, the tunnel is capable of serving both as a motorway and a flood channel, depending on the weather.

The Department of Irrigation and Drainage (DID) monitors river conditions to detect flood threats, while Amanat Lebuhraya Rakyat Berhad's (ALR) SMART Traffic Control Centre oversees traffic operations. When floodwater threatens to overwhelm the river system, the motorway section can be closed to traffic, allowing the tunnel to divert the excess water. This process involves activating Mode 3, which prepares the tunnel for flood mitigation, and potentially moving to Mode 4 if the rain persists.

Once the floodwater is diverted, it is stored in Taman Desa Pond and eventually released into Sungai Kerayong through a 500m-long twin box culvert. The gates provide access to the tunnel's interior, revealing a system of pumps and maintenance facilities. The Pump Room, located about 30m underground, houses five large pumps that drain the trapped floodwater.

After an operation, crews must clean the tunnel, remove debris, and repair any damage caused by the water. This process, which includes checking for gas and other hazards, typically takes two days with a target reopening within four days. The average repair costs amount to RM500,000.