FORGET the Shard; put aside the dome of St Paul’s Cathedral. Perhaps the greatest feat of engineering in London lies underground. Joseph Bazalgette’s sewerage network, built between 1859 and 1875, runs for about 21,000km (13,000 miles) underneath the city.
A mass of tunnels, archways and cavernous spaces, the sewers are largely unknown to Londoners, though they use them every day. But on September 12th the government approved a project which may match Bazalgette’s achievement. In doing so it highlighted how much a modern city still relies on Victorian ingenuity.
Sewers have long been a problem in London. Cesspits pockmarked the city in the 14th century; in 1326 Richard the Raker, a cleaner, fell into one and drowned “monstrously, in his own excrement”.
As London grew, so did the problem. By the 17th century sewage overran into the basements of houses. Bazalgette designed his sewers–a combined system, mixing water from drains with foul stuff–for a population of 3.5m, around a third more than lived in London at the time.
Some 8.4m people now live in London, and rising. Habits have changed, too, putting more pressure on the system, says Rob Smith, the chief flusher for Thames Water. People bathe more frequently; they are also awake at increasingly odd hours, lengthening the peaks of sewage flow Mr Smith and his team are used to dealing with. As the city grows, the Victorian system creaks.
Last year 55m tonnes of untreated sewage overflowed into the River Thames. The notoriously unreliable British weather adds to the problem: when your correspondent visited the dripping Fleet sewer last year, high-water marks could be made out on the walls at one overflow point, far above head-height–the legacy of one particularly rainy season.
The Thames Tideway Tunnel, which will cost around £4 billion ($7 billion) to build, will run 25km from Acton in west London to Abbey Mills, one of Bazalgette’s original pumping stations, in the East End. It will be nearly as wide as the Channel Tunnel, and parts of it will be the deepest tunnel ever bored in the city.
It will also come at a cost to Londoners, even those who live far from the 24 construction sites. Because so little has been done to improve the system over the years, water prices in the capital have been cheaper than elsewhere. Overflowing sewers were dealt with in places such as Bristol in the late 1990s; prices have been higher outside the capital as a result. That discrepancy will end as the tunnel adds about £80 to each household’s bill.
In its scope and vision, the “super-sewer” could match Bazalgette’s original. It is unglamorous and not a vote-winner, making it even more admirable that it is being pushed through. And if the tunnel-boring machines can start running by 2016, three years later than originally planned, that is not such a bad delay by historical standards.
It took six commissions between 1848 and 1855, as well as a cholera outbreak, to get Bazalgette’s sewers built. Modern planners might, for once, be more efficient than the Victorians.
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