To build Thames Water’s four-mile sewer tunnel, under east London, the German built machine will be taken apart and reassembled 80 metres below London, where it will construct the Lee Tunnel.

The £635m tunnel, will according to the water company, prevent 16 million tonnes of sewage entering the River Lee each year – a result of London’s Victorian sewers not being big enough to cope with heavy rainfall.

Tunnelling work is due to begin in January 2012 and is expected to finish in late 2013, with the machine cutting into about 17 metres of rock and dirt a day.

Thames Water’s head of capital delivery, Lawrence Gosden, said: “Tunnelling is a risky business, especially on a project of this scale, so it’s essential we use the best available technology and ensure every last detail meets our unique requirements.

“The Lee Tunnel is the first of two tunnels, which will collectively capture an average of 39 million tonnes a year of sewage from the 35 most polluting combined sewer overflows.

“The Lee Tunnel will tackle discharges from London’s largest overflow at Abbey Mills in Stratford, which accounts for 40 per cent of the total discharge. That’s why we’re dealing with this, the worst one, first.”

From mid-June, the tunnelling machine will be transported to London, where it will be reassembled in sections at Beckton sewage treatment works, before it is lowered into the ground.

The machine will be transported by barge via Germany’s River Rhine to Rotterdam then shipped across the North Sea to Tilbury, on the Thames estuary in Essex, before being driven overnight in bits by lorry to Beckton.

Luke Walsh

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