The Thames Tideway tunnel – a huge project to build a new super-sewer beneath London – reached a key milestone this week (June 20th ) as the first two of its six giant tunnel boring machines (TBMs) were lowered 53m into the ground.
The two TBMs, Millicent and Ursula, named after pioneering women who lived and worked in London close to Tideway’s sites, will be used to dig the central section of the 25km tunnel, which is being constructed to tackle the problem of sewage pollution in the River Thames.
The project, which is the largest of its kind ever carried out by the UK water industry, represents the most significant change to London’s sewers for more than 100 years. The existing Victorian sewer network was designed by Sir Joseph Bazalgette over 150 years ago for a city of up to four million people. Today London’s population is over eight million and growing fast.
The 7m diameter tunnel will run around 66m beneath the route of the Thames and connect to the combined sewer overflows (CSOs) that are located along its banks. These were originally designed to release overflow sewage into the river during heavy storms, but the strain that the ageing sewer system is now under means that this happens on a weekly basis even if there are no storms.
The new tunnel will intercept this waste before it enters the river, carrying it east towards the Lee Tunnel, which will transfer the sewage to Beckton Sewage Treatment Works.
During a complex and lengthy process, the two TBM cutterheads – which each weigh over 850 tonnes – were lowered to the bottom of a 53m shaft at a site in Kirtling Street site near Battersea Power Station. Once lowered the machines were placed into launch adits, otherwise known as starter tunnels, before work to complete the build of the TBMs, which will be over 100m long when fully built, begins in earnest. The TBMs will remain underground for almost two years as they dig the tunnels.
READ OUR ARCHIVE COVERAGE OF BAZALGETTE’S ORIGINAL LONDON SEWER
just goes to show “boring” – – – needn’t be! 🙂
Interesting article, look forward to further coverage as this project progresses.
Fascinating. How on earth did they get 7m diameter vessels at 850 tonnes through London?
We normally struggle if diameter (or height) exceeds 4.5 m! Bridges and street-furniture cause major problems ……. so scope for a further informative article! Even local construction would be difficult for such a vessel.
They are probably delivered in sections and assembled on site. French ingenuity no doubt!
The TBMs used on Crossrail were certainly delivered like this, except they were German-made.
The Crossrail Machines were transported in subsections and then assembled on site. I expect a similar strategy was used for these.
This stirred a memory of a request for some consultancy in fabric development probably 20-30 years ago. There was a suggestion that instead of tunnelling, as described above, a trench would be dug (I presume at the side on one bank of the River Thames) into which would be sunk concrete or steel sections , later covered over with the soil formerly removed. With a suitable geo-textile to protect such? I had had a project to assist with the development of fabric to ‘sleeve’ the inside(s) of existing brick sewers (the wish was to do so without the massive traffic disruption of having to dig-up the road!) and it was suggested that this technology might have application inside the ‘new’ side based tunnel.
Do I presume that they eventually opted for the present ‘normal’ tunnel described.
Wonderful skills and innovative thinking from Engineers projecting forwards with inspiration, not looking backwards for precedent? well described in this article.