Kuala Lumpur’s dual purpose tunnel is a world first
Kuala Lumpur’s Stormwater Management and Road Tunnel (SMART) is
a unique solution to the Malaysian capital’s long-term traffic and
stormwater management problems and the first tunnel of its kind in
the world. The dual-purpose tunnel will divert floodwaters away
from the confluence of the two major rivers running through the
city centre while its central section will double up as a two-deck
motorway to relieve traffic congestion at the main southern gateway
into the city centre.
SMART was originally conceived as a flood relief tunnel to divert
the 1 in 100 year flood away from the city centre. Then it was
considered that the 11.8m internal diameter tunnel could be
utilised in periods of low rainfall as a highway tunnel to
alleviate Kuala Lumpur’s congested highway infrastructure. Mott
MacDonald was approached by the MMC Engineering Group-Gamuda JV to
carry out the feasibility study for this innovative dual purpose
tunnel and then provide detailed design services to take the
project from concept through to construction, working in
association with SSP Consultants. The SMART project is now being
implemented under the supervision of Mott MacDonald/SSP on behalf
of the joint venture. The highway section is due for completion in
2005 and the bypass tunnel a year later.
The overall £335 million scheme comprises 9.5km of tunnel with the
central 3km incorporating a double deck motorway. Major components
include an upstream intake structure, holding pond and storage
reservoir, diversion tunnel, twin box culvert and ingress/egress
connectors to the motorway tunnel. Ventilation of the road tunnel
requires construction of four 15m-high shaft structures.
Three mode tunnel operation
SMART will work on a three mode system. Mode one operates under
normal conditions or when rainfall is low such that no water needs
to be diverted into the tunnel. Moderate storms activate mode two.
This will divert floodwater into a bypass tunnel in the lower
section of the motorway tunnel which will remain open to traffic.
During the once or twice yearly heavy storms a switch is made to
mode three when the tunnel is closed to road traffic and the full
tunnel section with a combined capacity of 3 million cubic metres
becomes available to divert the dramatically increased flows.
Extensive monitoring stations will ensure sufficient time is
allocated to allow the last vehicle to exit before the automated
watertight gates are opened. The motorway will then reopen to
traffic after clearing of the tunnel within 48 hours of closure.
We’re helping ensure that the change-over between modes from
vehicle to flood use is practical and efficient.
Ground conditions dictated construction by tunnel boring
machine which is now under way with two slurry TBMs working in
opposite directions from the middle of the tunnel alignment. We
helped develop the TBM procurement strategy and produce contract
documents to enable the contractor to purchase two 13.2m diameter
machines – among the world’s largest in diameter. A ventilation
shaft sited near central Kuala Lumpur served as the launch site for
the TBMs. The ventilation facilities are located in Limestone rock,
with the largest excavation being 150m in length, 20m wide and 28m
The first TBM launching shaft was completed in January 2004 ready
for assembly of the first TBM which commenced tunnel boring in June
2004. Shortly after this the second TBM arrived for assembly and
commissioning and began tunnelling in August 2004.