After 8 years of construction, the super sewer that can hold as much water as 600 Olympic swimming pools under London has been completed and will operate on a trial basis this summer.
The sewer pipe is so wide that it can fit three buses side by side. Image: Thames Tideway Tunnel
Called the Thames Tideway Tunnel, the project is designed to reduce the amount of raw sewage flowing into the River Thames. The 25km pipeline will divert 34 of the most polluted wastewater flows into the River Thames, with the BBC reported on March 27. According to Andy Mitchell, managing director of the Thames Tideway project, they will retain the vast majority of wastewater flowing into the river, making the Thames cleaner.
In the final step of construction, a massive 1.200-tonne concrete cap was placed over the pipeline in east London. London's combined wastewater system treats both human waste and stormwater, but the city's population strains the infrastructure. Under normal conditions, raw sewage would flow into the wastewater treatment plant, but today even a small drizzle in London can overflow the network, leading to floodwater flowing into the River Thames. Instead of flowing into rivers, the new super sewer will store almost all of central London's wastewater overflow until it can be treated.
As expected, the first wastewater flow will flow into the tunnel this summer. The project will be fully operational by 2025. While the initial expected cost was $5,3 billion, the tunnel cost about $6,3 billion. That cost will be paid by Thames Water customers over several decades.
The 7,2m wide tunnel slopes steadily from Acton in west London to Abbey Mills in the east. During periods of prolonged rain, the tunnel will contain a mixture of raw sewage and stormwater. The project can store as much liquid as 600 Olympic swimming pools, then pump it into Europe's largest wastewater treatment facility in Beckton, east London. After commissioning throughout the summer, the super sewer will be handed over to the water company Thames Water.
While the new super sewer is one of the biggest upgrades to London's sewer network since its construction by Joseph Bazalgette in the 1860s, it is certainly not a permanent solution. Scientists predict climate change will bring more heavy rain to the UK, meaning there will be a time when even the giant super sewer will be full.
London Waterkeeper activist Theo Thomas said authorities should spend money on projects across London to prevent rainwater from flowing directly into sewer pipes and mixing with raw sewage. Mitchell agreed with this view but said it was not feasible to quickly build a new network separating wastewater and stormwater in London at a reasonable cost.
An Khang (Follow with the BBC)
