London is undergoing the biggest modernization of its sewerage network and one of the biggest beneficiaries is going to be the Thames. With 7.2 meters in diameter and 25 kilometers long, a huge tunnel will put an end to the massive discharges of used water into the river.
Work on the 'super-sewer', as it is called in London, began seven years ago. Thousands of workers and engineers have worked on its construction under the soil of the British capital and the river itself. The tests of its operation will begin in 2024 and the following year, in 2025, it is expected to be fully operational.
The current sewage system dates from the 19th century. It was designed by engineer Joseph Bazalgette after the so-called 'Great Plague' of the summer 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.
The system designed by Bazalgette transported both used water and rainwater, so that the former usually ended up in the Thames. Taylor Geall, from the construction company that has designed the project, explains that every time it rains, even lightly, the sewer fills up and all the water ends up pouring into the river.
That is why, even if the previous brick system is intact, it is not enough for a population that has grown from four million to nine million people since the sewer system was built. "In a year, 40 million tonnes of wastewater flows into the Thames without any treatment," Geall says.
With the new system, the tunnel will carry wastewater only when the existing sewers are filled. The overflow points will allow wastewater to be diverted into the new tunnel and not end up in the Thames as it currently does. The objective is to intercept and eliminate 95% of the discharges.
"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," explains Taylor Geall. The cost of the works will be 5.02 million euros (4.3 million pounds sterling).
The last stages of the construction of this megaproject take place in the midst of controversy over the water sector, privatized in 1989, which has been accused of chronic underinvestment in its networks.
Thames Water, the London area water management company (serving 15m customers) was fined £3.3m in early July for polluting waterways. With a debt of almost 14,000 million pounds sterling (16,300 million euros), it is their clients who finance the 'super sewer' by deducting it from their bills.
According to the AFP news agency, Thames Water has already paid £32.4m in fines for pollution incidents in the Thames Valley and southwest London in lawsuits from other regulators between 2017 and 2021.
For Mathew Frith, of the conservation organization London Wildlife Trust, the new culvert will make a "great contribution" to the restoration of the Thames. But, he says, it will not solve the problem in other parts of the country, where used water is also dumped. According to the government's environmental agency, sewage spilled an average of 825 times a day last year into rivers and coastal areas across the UK.
