Tunnel link for Glasgow reservoirs

Published on Sunday 17 April 2005 01:14

ENGINEERS will this week drill through solid rock to link Glasgow’s two reservoirs with Scottish Water’s new £120m treatment plant at Milngavie.

Mugdock and Craigmaddie Reservoirs currently flow into Milngavie Water Treatment works, built 150 years ago. But the tunnel, to be completed by 2007, will feed into a new plant at Barrachan.

The work by specialist tunnellers, which will take nearly three months to complete, is part of a giant engineering jigsaw that Scottish Water says will bring Glasgow’s water supply into the 21st century.

Engineers believe the new technology will cut the risk of an outbreak of waterborne bacteria such as cryptosporidium. The bug was found in water at Mugdock three years ago, prompting ‘boil water’ notices to be issued and a massive health scare, because Scottish Water did not know which areas were supplied with water from the reservoir.

Under the plans, miners will drill down 100ft by hand through dolerite rock, sandstone and clay, before working sideways for another 50ft to allow a 49ft-wide tunnel to reach into Mugdock Reservoir.

Scottish Water chief executive Jon Hargreaves said: "This is one of the most challenging engineering projects Scottish Water has ever faced."

The tunnellers will artificially lower the water levels in Mugdock to allow them to work safely on the tunnel.

The work will see the water levels in Mugdock lowered by 33ft, often by only 1ft a day. This will remove 770 million gallons of water from Mugdock, leaving 110 million gallons and a water level of 282ft in the reservoir.

Once the work is completed, it could be several months before Mugdock is brought up to its present level of 318ft. This will mean that Mugdock will be out of commission for around six months, although contingency plans have been put in place to ensure customers’ supply continues from Craigmaddie and alternative sources.

Project manager Gus Watt said: "This is a very important stage in the largest construction project in Scotland. We are building on the engineering excellence that made this water supply for Glasgow possible in the Victorian age, when much was done for the city."