The Victorian Era

How Was the London Sewer System Built

Article · Science & Invention · The Victorian Era, 1837–1901

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The London sewer system, the network of 83 miles of main intercepting sewers, 1,300 miles of street sewers, four pumping stations, and two outfall works that still carries the sewage of central London to the treatment works at Beckton and Crossness, was built between 1859 and 1875 under the direction of Sir Joseph Bazalgette, the chief engineer of the Metropolitan Board of Works. The system was a response to the sanitary crisis of the What was the Great Stink of London?, the summer of 1858, and it was the largest public works project of the Victorian era, employing 20,000 navvies at its peak, using 318 million bricks, and costing some £4 million. The story of the sewers is part of the wider history of Victorian Engineering Marvels and Victorian Medicine and Public Health.

The Old Sewers

By the 1850s, the medieval and early modern sewers of London were no longer fit for purpose. The metropolitan area had grown from perhaps half a million people in 1800 to over 2.6 million in 1851, and the new flushing toilets, the underground water supplies, and the dense slum populations of the inner suburbs all added to the volume of sewage. The old brick sewers, built over centuries by the various local commissions, discharged directly into the Thames, often at high tide, and the result was a foul, fetid, and increasingly unhealthy river flowing through the heart of the city. The 1851 census recorded the population of the metropolitan area at 2,362,236, and the How did London’s population grow? of the period had outstripped the city’s ability to dispose of its waste.

The first proposals for a comprehensive new system had been put forward in the 1840s, and the Metropolitan Sewers Commission, established in 1848, had drawn up a scheme for a network of intercepting sewers. The chief engineer, John Phillips, and the engineer James Walker had worked out much of the technical basis, but the scheme had been blocked by the cost, by the rivalries between the existing 144 sewer authorities, and by the political instability of the period. The crisis of the Great Stink of 1858 finally forced Parliament to act.

Bazalgette’s Plan

Sir Joseph Bazalgette, born in Enfield in 1819, trained as a civil engineer under Marc Isambard Brunel and later under Thomas Telford’s pupil James Walker, had been appointed chief engineer of the Metropolitan Commission of Sewers in 1849 and of the Metropolitan Board of Works in 1856. By 1858, his plans were complete. The scheme was a network of three main intercepting sewers, the Northern, the Southern, and the Western, running on each side of the Thames and converging at two outfall works downstream of the city. The Northern Outfall Sewer ran from Hampstead Heath and Highbury to Beckton on the north bank of the Thames in east London. The Southern Outfall Sewer ran from Putney, through Bermondsey, to Crossness on the south bank in the Erith marshes. The Western Outfall Sewer ran from Kew, along the southern side of the river, and joined the Southern at the same point. The three mains were supplemented by 82 miles of branch intercepting sewers, 1,300 miles of street sewers, pumping stations, and the two outfall works.

Bazalgette’s calculation of the capacity of the new system was, by his own account, based on an estimate that the population of London might eventually reach six million, and he designed the sewers accordingly. The largest of the brick sewers, the Northern Outfall between Old Ford and Abbey Mills, was over nine feet high and almost as wide, and the system as a whole was designed to handle 200 million gallons of sewage a day. Bazalgette’s estimate that the system would be adequate for fifty years proved correct, and the major additions of the 1890s and 1900s were downstream of the original works.

The Construction

The construction of the new sewers was one of the great feats of Victorian engineering. The brick sewers, the largest of which were over nine feet high, were built of more than 318 million bricks and 670,000 cubic yards of concrete. The work was done largely by hand, by gangs of navvies working in shifts in the deep cuttings through the soft ground of the Thames valley, and the conditions were often dangerous. The use of the steam-driven pumping engine, the new hydraulic cement, and the new iron-shod navvy bucket and steam crane all reduced the labour, but the work was still, in modern terms, a hand-dug tunnel.

The project also required the construction of four new pumping stations, the Pimlico, the Western, the Southern, and the Abbey Mills pumping stations, the new embankments of the Thames at Chelsea (1874), the Victoria (1870), and the Albert (1869-70), the new bridges at Chelsea, the Victoria, the Albert, and Battersea, and the new streets that ran on top of the embankments. The embankments, which were partly a flood-prevention measure and partly a transport project, were Bazalgette’s own design, and they were a substantial piece of the public works. The embankment reclaimed 52 acres from the river, carried the new Metropolitan District Railway, and provided a new riverside road, the Victoria Embankment, that ran from Westminster to Blackfriars.

The Outfall Works

The two great outfall works, at Beckton on the north bank and at Crossness on the south bank, were the largest and most elaborate buildings of the whole scheme. The Crossness works, opened in 1865, included the famous octagonal engine house designed by Bazalgette in collaboration with the architect Charles Driver, a magnificent example of High Victorian Gothic architecture. The Crossness engine house contained four of the largest beam engines in the world, each capable of pumping 25 million gallons of sewage a day, and the building was decorated with elaborate ironwork and ornamental tiles that have been compared to the Albert Memorial. The Beckton works on the north bank, opened in the same year, were equally impressive, and the Abbey Mills pumping station, opened in 1868, has been called the “cathedral of sewage” for the extraordinary Gothic design of its exterior, with the four chimneys that were the model for T. S. Eliot’s typist in The Waste Land.

The two outfall works were designed to discharge the sewage into the river at high tide, so that it would be carried out to sea on the ebb tide, and the works were fitted out with the latest pumping machinery of the period. The disposal of the sewage downstream of the city, however, created a new problem. The discharge of the sewage at Beckton and Crossness poisoned the river downstream and destroyed the fishing and the shipping of the lower Thames, and it was not until the late nineteenth and early twentieth centuries that chemical treatment and biological filtration were added to the outfall works.

The Cost and the Legacy

The cost of the new sewers, paid for out of loans raised by the Metropolitan Board of Works, was some £4 million, raised in successive tranches between 1858 and 1875. The work was completed in 1875, and the new sewers transformed the public health of London. The last great cholera epidemic in London was in 1866, just two years after the first section of the new system was opened, and the disease never returned to the capital in epidemic form. The incidence of typhoid fell dramatically, the infant mortality rate began to decline, and the average life expectancy of the Londoner rose substantially over the second half of the nineteenth century.

Bazalgette’s other works in this period included the Chelsea Embankment (1874), the Victoria Embankment (1870), the Albert Embankment (1869-70), the Putney Bridge (1886, replacing an older structure), the Hammersmith Bridge (1887, replacing an earlier toll bridge), and the early plans for the Hammersmith flyover. The new embankments, the new bridges, and the new pumping stations together transformed the appearance of central London and made the modern city possible. The new sewers were a triumph of Victorian Engineering Marvels, and they remain one of the great monuments of the Victorian era. Bazalgette was created a baronet in 1886, served on many Royal Commissions, and was widely honoured in his own lifetime. He died in 1891, three years after his retirement, and his statue stands beside the Victoria Embankment, looking down on the river that his sewers helped to clean.