ICE Award For Costain
22 April 2010
The Thames Water Ring Main Extension Project has
received a special award from the Institution of Civil Engineers
for its work helping to ensure the future resilience of London's
water supply.
The project has seen several major contractors, including
Costain, driving nearly 10km of new tunnels plus four
large-diameter pump-out shafts through some of the capital's most
congested areas - both above and below ground.
The aim was to increase the Ring Main's capacity by 500 million
litres per day, without adversely affecting further extensions in
the future. This was to be achieved without any road closures,
transport suspensions or interruption to amenities.
The Costain team based at the Hampton Advanced Water Treatment
Works in southwest London was responsible for sinking one of the
major shafts and tunnelled connections to an existing Ring Main
shaft and the High Lift Pumping Station. The shaft was 15m in
diameter and 40 metres deep. The connecting tunnels were
constructed either by open-face heading or using a Costain Tunnel
Boring Machine.
Ground conditions were an initial problem, with an unexpected
substantial brick Victorian pumping station three metres below the
surface whose foundations extended a further six metres down. The
team also had to contend with contaminated ground and the diversion
of multiple utilities.
The shaft was constructed using traditional underpinning methods
through the historically disturbed ground, followed by an
innovative design employing a sprayed concrete lining (SCL) for the
remaining two-thirds. The SCL was a value engineering/contractor
proposal comprising two layers of sprayed concrete which sandwiched
a spray applied water-proofing membrane.
This alternative method provided benefits in cost and programme
where the tunnel portal construction was considerably
simplified.
ICE judge Chris Wise, speaking at the 2010 London ICE Awards
where the special prize was presented to the teams involved in the
10km extension project, commented: "At 80km long, the Ring Main's
achievements were already breathtaking and fundamentally underpin
life in this city as we know it.
"With these four new extension projects the water supply will be
even better, giving greater certainty, greater resilience, using
less energy and extending both its usefulness and its
sustainability."