The tunnel stretches 25 kilometers along the River Thames in London (AFP/Daniel LEAL)
For seven years, thousands of workers and engineers have worked on the construction, under London and the Thames, of an enormous tunnel 25 kilometers long: it must make it possible to modernize the sewers of the 19th century, to finally stop massive waste water discharges into the river.
The tunnel, with a diameter of 7.2 meters, winds from west to east following the curves of the Thames. This “super-sewer”, as it is called in the UK, is to be tested in 2024 and fully operational by 2025.
It’s the biggest modernization of London’s sewer system since the second half of the 19th century, at the time designed by engineer Joseph Bazalgette after the infamous ‘Great Stink’ of 1858.
In July and August of that year, the combination of high temperatures and sewage flowing directly into the Thames plunged the city into a cloud of putrid air.
Work took seven years on what is the biggest sewer modernization since the 19th century (AFP/Daniel LEAL)
But in recent decades, sewage has once again flowed into the river, due to lack of sewer capacity in the face of the British capital’s growing population.
Joseph Bazalgette’s sewerage system, a masterpiece of 19th century engineering, carried both sewage and rainwater, so the former often flowed into the Thames.
– “No treatment” –
Workers must descend more than 40 meters vertically into a well (AFP / Daniel LEAL)
“Every time it rains, even a light drizzle, the drains fill up and flow straight into the river,” says Taylor Geall of construction company Tideway, which is behind the project. “In an average year, 40 million tonnes of sewage flow into the Thames without any treatment.”
The old brick sewers are still in perfect condition, but they are not big enough.
The network was built when London had a population of four million, compared to nine million today.
The modernization, the cost of which amounts to 4.3 billion pounds sterling (5.02 billion euros), had become necessary.
The new tunnel will carry sewage only when the existing sewers are filled. Overflow points will allow waste water, which under the current system would have flowed into the Thames, to be diverted to the new tunnel.
Seven meters in diameter, the tunnel must prevent the overflow from flowing into the Thames (AFP / Daniel LEAL)
“We will intercept and eliminate 95% of spills,” says Taylor Geall. “Once we’re done, the river won’t look much different, but it will provide a much healthier environment for the fish, marine mammals and birds that live there.”
– Closed beaches –
The last stages of the construction of this megaproject are taking place in the midst of controversy for the water sector, privatized in 1989, and accused of chronic under-investment in its networks.
According to the government environment agency, sewage spilled an average of 825 times a day last year into rivers and coastal areas across the UK.
Methane and oxygen levels in the air are monitored during the construction of the tunnel (AFP/Daniel LEAL)
Several beaches on the Isle of Wight, on the south coast of England, had to close during last summer’s heatwave due to high levels of bacteria in the water.
Surfers Against Sewage recently released a list of 83 beaches to avoid across the country due to sewage spills.
The government announced this week that water companies, along with other energy and waste operators, will face unlimited fines for polluting activities.
Thames Water, the London-area water management company that serves 15 million customers, was fined £3.3 million in early July for polluting waterways.
It is indebted to the tune of nearly 14 billion pounds sterling (16.3 billion euros). It is its customers who finance the “super-sewer” by deduction from their bills.
The statue of Saint Barbara, patron saint of tunnel boring machines, watches over the construction site (AFP / Daniel LEAL)
According to the PA news agency, Thames Water has already paid £32.4million in fines for pollution incidents in the Thames Valley and south-west London in other regulators’ lawsuits between 2017 and 2021.
For Mathew Frith, of the conservation organization London Wildlife Trust, the new sewer will make a “major contribution” to the restoration of the Thames. But, he says, it won’t solve the problem elsewhere in the country.
© 2023 AFP
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