Busy Lizzie, a 120m long Herrenknecht TBM, last night completed its journey from Germany to Beckton sewage works in east London, ready to start work on the US$1bn Lee Tunnel, a 6.4km sewer to help prevent 16M tonnes of sewage entering the river annually during heavy rainfall.
Since June, the machine has been transported by barge in sections via Germany’s River Rhine to Rotterdam before being shipped across the North Sea to Tilbury, on the Thames estuary in Essex, from where it was driven overnight via the A13 road to Beckton.
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Last night the largest piece of the machine – the 8m diameter cutter head – arrived in four parts, under police escort. Ahead of the machine’s arrival, street signs and lamp-posts were moved temporarily to enable the wide load to get past. It will be reassembled 80m below London, where it will start work in January 2012.
Lawrence Gosden, Thames Water’s head of capital delivery, said, “We face the challenge of boring the deepest tunnel in London at some of the highest groundwater pressures that a machine of this type has ever tunnelled in. We will be passing through four miles of the most abrasive ground without any other shafts along the way.
“The Lee Tunnel is the first of two tunnels, which will collectively capture an average of 39M tonnes a year of sewage from London’s 35 most polluting combined sewer overflows. The Lee Tunnel will tackle discharges from the largest overflow at Abbey Mills in Stratford, which accounts for 40% of the total discharge. That’s why we’re dealing with this, the worst one, first.”
During heavy rainfall when London’s Victorian sewers reach capacity, there is simply nowhere else for the remaining sewage to go. Beckton sewage works is being expanded by 60% to enable it to cope with the increased volume of sewage the tunnel will capture.
Tunnelling work is due to begin in January 2012 and is expected to finish in late 2013. The machine is likely to progress at a rate of 17m a day.
MVB, made up of three of the country’s leading civil engineering contractors – Morgan Sindall, VINCI Construction Grands Projets and Bachy Soletanche – are working together to deliver the Lee Tunnel.