By Scott Young, Education and Community Investment Executive for Thames Tideway Tunnel
In the UK, construction of London’s main sewerage system started way back in 1859. This was just a year before the election of Abraham Lincoln as President of the United States.
It’s amazing to think that today much of that network remains operational and is in surprisingly good condition for its age.
But that system is under increasing strain. London faces challenges similar to those you might have identified in designing your Future City:
- A growing population puts pressure on water and wastewater infrastructure
- Natural drainage is replaced by impermeable surfaces like roads, parking lots and buildings
- Natural features like London’s famous River Thames is under increasing threat from pollution
For too long, these issues have not been tackled in London.
When it rains sewage often overflows from the sewerage system into the tidal River Thames causing damage to the river’s wildlife and posing a health risk to those that use the river for leisure or business.
It’s a problem London faced in the past too. In 1858 the British summer was unusually hot. In those days the River Thames was an open sewer and the warm weather encouraged bacteria to thrive. The smell this created was so overwhelming that Parliament made plans to relocate to another city.
The “Great Stink” crisis resulted in Sir Joseph Bazalgette being appointed to build a system of interceptor sewers. He came up with a series of ingenious solutions for his “Future London City.”
He significantly increased the capacity of the sewerage system predicting that the population of London would grow. At the time London had 2 million residents. Today it has 8 million.
He also built in a safety mechanism so that when it rained and the system filled to capacity, sewage would flow out of overflow points – called Combined Sewer Overflows (CSOs) – positioned along the river. This prevented sewage backing up in to streets and homes.
His foresight has allowed London’s infrastructure to last to the modern day. But it is increasingly under strain, with pollution entering the tidal River Thames as often as once a week after as little as 2mm of rainfall.
It shouldn’t require another Great Stink before these problems are addressed.
Thames Water, the company responsible for managing drinking water and wastewater in London, is working with CH2M HILL engineers to design a solution – the Thames Tideway Tunnel.
The fifteen mile long tunnel, as wide as three London buses side by side, will capture sewage from the 34 most polluting CSOs. It will be stored and then transferred to a sewage treatment plant for processing.
Construction will last for seven years and involve work at 24 sites along the river.
A major project like this means working closely with residents, business, politicians and other organisations to address concerns and reassure people that our proposals work and provide value for money.
But it also means some disruption for those close to our work sites.
However, once the Thames Tideway Tunnel is completed in 2023, overflows into the tidal River Thames will be reduced by around 95 percent.
Learning lessons from past experiences like the Great Stink can be really helpful in responding to the challenges we might face in our cities of the future.
London has grown massively over the last 200 years. The growth has meant an increased strain on natural resources and our ability to protect them.
It’s important that once we’ve addressed the issue of sewage overflows in the tidal River Thames through the construction of the Thames Tideway Tunnel we ensure the river is protected for future generations.
That means promoting other solutions that will prolong the life of the tunnel and reduce the amount of water entering the sewerage system. Sustainable Urban Drainage systems (or SUDs) can stop water getting into the sewerage network as quickly by reducing the amount of impervious surfaces across an area and capturing storm water for reuse.
In designing your Future City, how might you avoid some of the difficulties London has faced in the past and can the solutions our engineers are proposing for London help you with your project?
To find out more about the Thames Tideway Tunnel watch this video on our plans.
CH2M HILL is serving as the program manager for the Thames Tideway Tunnel to modernize London’s 150-year-old sewer system, which will include tunnel diameters wider than three of infamous London double-decker buses placed side-by-side.