Architecture

Work begins on London's huge "super sewer" construction project

Work begins on London's huge "...
A crane has been moved into place at Blackfriars on the River Thames, signaling the start of work on the Thames Tideway Tunnel
A crane has been moved into place at Blackfriars on the River Thames, signaling the start of work on the Thames Tideway Tunnel
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A crane has been moved into place at Blackfriars on the River Thames, signaling the start of work on the Thames Tideway Tunnel
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A crane has been moved into place at Blackfriars on the River Thames, signaling the start of work on the Thames Tideway Tunnel
The Thames Tideway Tunnel will connect to the Lee Tunnel, which is already under construction
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The Thames Tideway Tunnel will connect to the Lee Tunnel, which is already under construction
The Busy Lizzie tunnel boring machine is lowered into place for the construction of the Lee Tunnel
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The Busy Lizzie tunnel boring machine is lowered into place for the construction of the Lee Tunnel
The tunnel boring machines both excavate and lay concrete segments around the freshly dug tunnel as they go
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The tunnel boring machines both excavate and lay concrete segments around the freshly dug tunnel as they go
There are 50 Combined Sewage Overflows along the River Thames, including this one pictured in Brixton
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There are 50 Combined Sewage Overflows along the River Thames, including this one pictured in Brixton
The Combined Sewage Overflows currently discharge over 39,500,000 cu m (1,400,000,000 cu ft) of sewage into the River Thames each year
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The Combined Sewage Overflows currently discharge over 39,500,000 cu m (1,400,000,000 cu ft) of sewage into the River Thames each year
The proposed route of the Thames Tideway Tunnel
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The proposed route of the Thames Tideway Tunnel
A map of the Combined Sewage Overflows along the River Thames
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A map of the Combined Sewage Overflows along the River Thames
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London, UK, has embarked on what is described as a "one in one-hundred-and-fifty-year project." The maneuvering of a crane into place at Blackfriars on the River Thames marks the start of major work on the Thames Tideway Tunnel, a "super sewer" that will drastically reduce sewage overflow into the river.

Large parts of London's sewer system were constructed over 150 years ago by Sir Joseph Bazalgette. Although the brick-constructed tunnels are said to still be structurally sound, they were not built to manage the capacity that is required today.

In the 1860s, during the construction of Bazalgette's sewer system, London had a population of around two million. Today, the population is over eight million. Not only is more sewage produced and more water used, but there is also less green space to soak up rainwater.

Bazalgette's combined sewer system was designed to carry both foul-water and rainwater away to be treated at sewage works around London. As part of of the system, he built in Combined Sewage Overflow (CSO) points on the banks of the river into the River Thames through which overflow runoff could be discharged in the event of the system becoming over capacity.

There are 50 Combined Sewage Overflows along the River Thames, including this one pictured in Brixton
There are 50 Combined Sewage Overflows along the River Thames, including this one pictured in Brixton

While they were designed to stop streets and homes flooding with sewage on the rare occasions it was necessary, the CSOs are now opened on average once a week and over 39,500,000 cu m (1,400,000,000 cu ft) of sewage is emptied into the River Thames as a result each year. The Thames Tideway Tunnel is aimed at reducing this output to around 2,400,000 cu m (84,800,000 cu ft).

The £4.2 billion (US$6.3 bn), seven-year project project will see a 25-km (16-mi) tunnel constructed that will run west to east from Acton to Abbey Mills, generally following the route of the Thames. From there, it will be connected to the Lee Tunnel, which is already under construction and will transfer the sewage to Beckton Sewage Treatment Works.

This scale of the required construction and tunneling is comparable to that of the recently completed Crossrail tunnels, although those are longer still. The Thames Tideway Tunnel will be 7 m (23 ft) in diameter and will be built between 25 m (82 ft) and 65 m (213 ft) below ground.

The Busy Lizzie tunnel boring machine is lowered into place for the construction of the Lee Tunnel
The Busy Lizzie tunnel boring machine is lowered into place for the construction of the Lee Tunnel

There are 50 CSOs along the Thames in total and the new tunnel will link the 34 most polluting outlets, siphoning away sewage that would otherwise have been directed into the river. The system will also act as a huge storage tank, capable of containing up to 1,600,000 cu m (56,500,000 cu ft) of sewage until it can be treated.

There will be 24 sites across London during the construction of the tunnel, with three main "drive sites" where tunnel boring machines (TBMs) are lowered into the ground. Preparation of the sites will include setting up offices and barge facilities, after which a vertical shaft will be dug from which the tunneling will start.

Tunneling will be undertaken 24 hours a day and will be taking place at several different sites at any one time. Much like those used for the construction of the Crossrail tunnels, the TBMs will both excavate and lay concrete segments around the freshly dug tunnel as they go. A concrete coating will be added to complete the process.

The Thames Tideway Tunnel will connect to the Lee Tunnel, which is already under construction
The Thames Tideway Tunnel will connect to the Lee Tunnel, which is already under construction

The tunnel is designed to get a meter (3.3 ft) deeper for every 790 m (2,592 ft) that it travels, so as to allow the sewage to flow naturally from one end to the other. In addition, it must dodge other existing tunnels underneath London, such as those for the Underground train lines. Excavated material will be transported out of the tunnels, processed and loaded onto barges for removal.

The crane at Blackfriars is being used to construct a new pier for Thames Clipper users, which is being moved to accommodate the tunnel construction. Despite only being of significance because it signals that start of major work, getting the crane into position was described as "no mean feat."

"The 20-m (66-ft) wide barge had to be carefully threaded under seven bridges and through the traffic on one of the busiest working rivers in the world," explains central project delivery manager for Tideway Andy Alder. "Alongside the man-made challenges, the crane also needed perfect tidal water levels and good weather before the movement could go ahead."

Tunneling activity for the Thames Tideway Tunnel is expected to begin in 2017 and to be completed by 2021. The tunnel is scheduled to be fully complete by 2023.

The video below provides an overview of the Thames Tideway Tunnel project.

Source: Thames Tideway Tunnel

You Poo Too

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4 comments
Bob Flint
So do you still want to swim or skate on the Thames Cesspool?? Not in this century..
Erg
And it still wont entirely solve the problem. The Thames, what a dump.
habakak
The girls math is off. Or her accent. Which would be my fault! But 8 million people on average pooping once a day (I'm more a 3 times a week kinda guy) would be 3.068 million kilos (*) a day (she states 1.25 BILLION kilos). A big difference. Now maybe her math includes all the water content too, but it's not 1.25 billion kilos of poop for sure.
* She states 140 kilos per person per year. So 140 x 8,000,000 / 365 gives you the daily amount of poop for the city.
Cyberxbx
"its good for a 100 years or so![from the video]"...... but its not...
"The Thames Tideway Tunnel is aimed at reducing this output to around 2,400,000 cu m (84,800,000 cu ft)"
So at no point would it ever stop dumping into the river.... and 100 years later, you will be back up to the "over 39,500,000 cu m (1,400,000,000 cu ft) of sewage" and have this problem all over again. What I would like to know is why wasn't this issue resolved when the population spiked back in the early 1900's? or even lat 1900's?
https://www.washingtonpost.com/news/worldviews/wp/2015/01/07/chart-londons-population-is-finally-about-to-return-to-its-1939-peak/
This seems to be a case of too little too late. They better be simultaneously sponsoring a low flow toilet/shower/sink concept, HE dishwasher/washing machine, and possibly rainwater collection to mitigate the flow into the system.

Lastly, think about this.... how much sewage would you deem acceptable to back up into your bathtub or sink......