Bazalgette and the sewers of London
How a Victorian engineer rid the capital of its waste, and of a deadly disease
In 1801 about one million people lived in London, which made it the largest city in Europe. By 1851 the figure was well over two million, and the arrangements for dealing with human waste, which had been barely adequate for a smaller town, had broken down. Most houses had a cesspit beneath the cellar floor, which was emptied from time to time by workmen who sold the contents to farmers as manure. As the city spread, however, the farms retreated further away, the pits overflowed, and the waste seeped into the ground and the streets.
The introduction of the water closet made matters worse. A flushing toilet uses far more water than a cesspit can hold, and the surplus ran out into the old drains, which had been built to carry away rainwater and which emptied into the Thames. Householders were soon encouraged, and eventually required, to connect to them. The river thus became an open sewer. Yet the same river supplied drinking water, since the companies that sold it to Londoners took it directly from the Thames, often at places where the tide carried sewage past their intakes.
The consequences were deadly. Cholera reached Britain from India in 1831 and returned in 1848 and again in 1853, killing tens of thousands of Londoners. Almost everyone, including most doctors, believed that the disease was carried by foul air, or 'miasma', rising from rotting waste. John Snow, a London physician, was unconvinced. During the outbreak of 1854 he marked the deaths in Soho on a map and found that they clustered around a public water pump in Broad Street. He persuaded the local authorities to remove its handle, but the epidemic was already declining, and few officials were convinced.
It was the smell, rather than the disease, that finally forced action. In the hot, dry summer of 1858 the level of the Thames fell and the sewage that had been poured into it lay rotting in the sun. The stench was so overpowering that the curtains at the Houses of Parliament were soaked in chloride of lime in an attempt to keep it out. Legislators who had argued over rival schemes for years suddenly found that they could not ignore the problem, and within weeks a law was passed authorising the Metropolitan Board of Works to build a new system and to borrow three million pounds to pay for it. The newspapers called that summer 'the Great Stink'.
The Board's chief engineer, Joseph Bazalgette, was given the task. Born in 1819, he had spent several years working on London's drainage. Rather than attempt to clean the Thames, he proposed to stop the sewage from reaching it. A series of large intercepting sewers would run roughly parallel with the river on both banks, collecting the contents of the old drains and carrying them eastwards, by gravity wherever possible and with the help of pumps where it was not, to outfalls at Beckton and Crossness, far below the built-up area. Bazalgette designed the system to serve four million people, a good deal more than lived in London at the time.
Work began in 1859 and gave employment to thousands of labourers. Most of the sewers were built of brick, more than 300 million of them, and Bazalgette insisted that the cement be tested for strength before it was used. Because much of London is low-lying, the sewage could not flow all the way to the outfalls under gravity and had to be lifted at several pumping stations. The largest of these housed great steam engines, and the buildings were so elaborately decorated that they were sometimes compared with churches.
The project also changed the face of the city. To make room for the northern sewers, the engineers reclaimed land from the river, and on it they built the Victoria Embankment, completed in 1870. Beneath its broad new road ran an underground railway and pipes for gas and water, as well as a sewer. Two further embankments, the Albert and the Chelsea, followed.
The effect on public health was dramatic. Cholera returned to London once more, in 1866, but it struck only the East End, where the new sewers had not yet been connected and where the water company's supply had become contaminated. It killed several thousand people, and it was the last major outbreak in the capital. Not everything had been solved. The new system carried sewage away from the city but did not purify it, so that the river downstream remained heavily polluted, and it was only in the following decades that treatment works were built to clean the sewage before it was released into the Thames.
Bazalgette was knighted in 1875 and died in 1891. His sewers are still in use, although London now has more than twice as many inhabitants as he allowed for, and heavy rain can force the overloaded network to discharge into the river. To relieve it, a new tunnel about 25 kilometres long has been built beneath the Thames. Meanwhile, the pumping station at Crossness, where the original engines have been preserved and restored, has become a museum. The system has lasted for a century and a half largely because Bazalgette allowed so generously for growth.