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Smart tunnel: Two issues, one solution

Mohd. Noor b. Mohd Ali
Head – Toll Ops & Public Relations
Syartikat Mengurus Air Banjir & Terowong SDN
BHD (The Stormwater Management & Road Tunnel)
[email protected]

The Stormwater Management and Road Tunnel (SMART) in Kuala Lumpur serves the dual purpose of flood mitigation and easing road congestion

Kuala Lumpur is a booming city and a nerve centre for Malaysia’s economy. Topographically, Kuala Lumpur was built along the flood plains of the Klang River and thus, since the earliest days it was subjected to flooding. In 1971, the flood lasted for five days and resulted in extensive damage. About 445 hectares of land in the city were inundated and the cost of damage was estimated to be in the region of RM36 million. Over the past decades, incidences of flooding have become more rampant and according to a recent study, the cost of damage due to floods to the whole country is around RM1 billion a year out of which RM100 million is borne by Kuala Lumpur city centre alone. Besides the risk of flooding affecting the city centre, Kuala Lumpur has also been experiencing road congestion issue due to the booming growth in its economic activities. One of the critical road alignments heading towards and from the city centre is the southern gateway link that connects the city to the southern part of the country. The traffic volume on this stretch has seen a huge growth and an alternative route to cater to further growth was greatly needed.

To address both these issues, MMC-Gamuda Joint Venture presented the idea of incorporating two major infrastructure components into one mega structure to the Government of Malaysia which gave the project a go ahead in 2003.

Smart features
The Stormwater Management and Road Tunnel, better known as SMART, started construction work in January 2003. The project demanded the effort and expertise of many – from supply of two slurry mixshield tunnel boring machines (TBMs) of more than 13 metre diameter to solving the complex engineering issues of combining two different uses in one tunnel, from supply of bentonite and M&E fittings to employing the workforce and the services of international and domestic leaders in their field. Part of the challenge was dealing with the soil condition of Kuala Lumpur which mostly consists of karstic limestone and alluvium with many cavities and pinnacles.

Hence, managing advance of the tunneling machines and progressing major surface and open cut works to refining the operating standards and protocols for the safest operations of the dual purpose facilities were of utmost importance.

Early results of the 3D modelling of reflected features at up to 40 m ahead were promising but the necessary sensors on the rotating cutterhead didn’t survive the harsh environment of the limestone excavation process and had to be removed and improvement was made onto the casing for better and more robust protection. Being able to “see” ahead of the tunnel face however remained a high profile objective and therefore other methods of geotechnical survey techniques were also applied, such as microgravity, cross hole seismic survey, ground penetrating radar and 2D resistivity tomography. The most beneficial of these was resistivity, a technique that detects changing resistivity of features within the ground to identify potential anomalies such as karst voids and fissured rock.

Mechanical and electrical components
Smart Tunnel is a dual purpose tunnel, incorporating a double deck motorway within the middle section of a stormwater tunnel. It was completed on 30 June, 2007. The completion of the Smart Tunnel is attributed to the implementation of innovative technologies and skilled team players. Being the first of its kind in its concept as a whole, there were indeed many firsts for the Smart team. In dealing with the dual purpose tunnel, amongst the most important components are the M&E equipment that can withstand the dual environment conditions – both wet and dry.

Smart operations
Smart Tunnel is designed first and foremost for flood control and as such stormwater operation mode will always over-ride the motorway operation mode. To ensure this protocol is maintained, the decision to close the motorway section for flood operation has been retained with the Government through its agency, Department of Irrigation and Drainage, Malaysia (DID).

Three modes of operation:
Mode 1 – no storm. For most time of the year, there is no storm or low rainfall, which means no diversion of water flow from the upstream confluence of the Klang River and Ampang River through Smart infrastructure to the attenuation pond downstream in Taman Desa. During this mode, the road section operates normally and the traffic is able to use the tunnel from Kuala Lumpur city centre – Seremban Highway and vice versa. There is no discharge of water into the tunnel in this mode.

Mode 2 – minor storm. When there are moderate or minor storms and the river flow at the confluence exceeds 70 cumec (cubic meter per second), the Stormwater Tunnel is activated to “semi-open” status by allowing diversion of water flow from the confluence of Klang and Ampang rivers to the storage pond located upstream in Kg Berembang, Ampang, thereafter into the tunnel, and through the lowest channel of the road tunnel section and into the attenuation pond downstream in Taman Desa.

The flood detection system (FDS) operated by DID continuously and closely monitors any changes in weather conditions. The motorway section operates normally where there is no traffic disruption for those driving through the tunnel since only the lowest channel is being used at this juncture.

Mode 3 – major storm. When the FDS detects a reading at the river confluence of more than 150 cumec and predicts heavy and prolonged downpour, the Stormwater tunnel is activated to “fully open” status. The radial gates at the diversion weir are lowered to divert water flow in full capacity from the confluence of two rivers into the holding pond. At the same time, the entrances to the motorway section are closed to traffic while all vehicles in the tunnel are evacuated.

This is to ensure that both the road decks are empty and ready for flood water to be channelled through the tunnel to the attenuation pond. Sufficient time is allocated to ensure that all traffic is evacuated before all the relevant gates such as the road gates, service gates and emergency gates are activated to allow the water to be diverted through the tunnel.

Once the FDS indicates that the Mode 3 status is over and the weather is back to normal, flood water is pumped out of the tunnel into the attenuation pond and the tunnel is cleaned of mud and small debris. In normal process of cleaning and inspection of the tunnel condition, Smart tunnel is reinstated within 48 hours after the water channelisation is made and traffic for the motorway section is allowed back for usage as normal thereafter.

Smart benefits
After operating for more than three years, Smart tunnel has proven to be a success in meeting its primary and secondary objectives. Through the Smart tunnel, areas such as Masjid Jamek area, Dataran Merdeka, Leboh Ampang and Jalan Melaka have witnessed no flooding incidence since 2007.

In monetary terms, the tunnel has managed to save around RM112 million, based on the number of possible major floods that could affect these areas should there be no such infrastructure in place for Kuala Lumpur city centre.

As for the traffic relief, Smart Tunnel has been widely accepted as one of the preferred alternative by road users for their journey into the Kuala Lumpur city centre from the southern gateway and vice versa. The major reason for that is the travelling time which has been minimised from the normal 20 minutes when using the federal road to only eight minutes when using the Smart Tunnel.

Besides these benefits, Smart Tunnel project has also managed to develop more experts in the tunneling job where from the project alone, it has groomed up to 200 local engineers who are now capable of taking up any tunneling challenges anywhere in the world.