The Thames Tideway Tunnel - a colossal 15 mile underground concrete tube stretched out across London - will enable nature to return to the longest river in England.
After seven years in the making, the “super sewer” is nearly finished, and ready to stop an annual 40 million tonnes of sewage spilling into the Thames, helping to transform the capital’s river and make the water fit for the return of otters, fish and even seals.
If the project fulfils its ambitions, it will not only bring the kind of wildlife back to the Thames not seen for over two centuries, but reconnect human-life to their river too. Coincidentally, the River Seine in Paris is also in the midst of a multi-billion clean up restoration too - ready for next year's Olympics.
Eight new public parks are being built over the top of the access shafts in London. Several will have tidal beds that fill with water and drain away as the river falls and rises throughout the day, replicating long-lost ecosystems.
“We always knew the physical job we had to do,” says Andy Mitchell, Tideway chief executive. “But we can also see that there is something else we can contribute, which is a greater appreciation of the river. “It’s a neglected, a broken relationship [between Londoners and the Thames], a lost love affair.”
The tunnel’s capacity is immense, at 1.6 million cubic metres when absolutely full. Not only will it be able to take all that liquid to the treatment works in east London, but it will be able to store it, acting as a giant reservoir while the sewage works handle the backlog.
If all goes to plan, the 60 or so discharges a year that happen to the Thames should fall to perhaps four or less spills each year - and nature will be able flourish once more.