The London sewer system is part of the water infrastructure serving London, England. The modern system was developed during the late 19th century, and as London has grown the system has been expanded. It is currently owned and operated by Thames Water and serves almost all of Greater London.
During the early 19th century the River Thames was an open sewer, with disastrous consequences for public health in London, including cholera epidemics. These were caused by enterotoxin-producing strains of the bacterium Vibrio cholerae . Although the contamination of the water supply was correctly diagnosed by Dr John Snow in 1849 as the method of communication, up to the outbreak of 1866 it was believed that miasma, or bad air, was responsible. [1] Proposals to modernise the sewerage system had been made in the early 1700s but the costs of such a project deterred progress. Further proposals followed in 1856, but were again neglected due to the costs. However, after the Great Stink of 1858, Parliament realised the urgency of the problem and resolved to create a modern sewerage system. [2]
Joseph Bazalgette, a civil engineer and Chief Engineer of the Metropolitan Board of Works, was given responsibility for the work. He and his colleagues, including William Haywood, designed an extensive underground sewerage system that diverted waste to the Thames Estuary, downstream of the main centre of population. Six main interceptor sewers, totalling almost 160 km (100 miles) in length, were constructed, some incorporating stretches of London's "lost" rivers. Three of these sewers were north of the river, the southernmost, low-level one being incorporated in the Thames Embankment. The Embankment also allowed new roads, new public gardens, and the Circle line of the London Underground. Victoria Embankment was finally officially opened on 13 July 1870. [3] [4]
The intercepting sewers, constructed between 1859 and 1865, were fed by 450 miles (720 km) of main sewers that, in turn, conveyed the contents of some 13,000 miles (21,000 km) of smaller local sewers. Construction of the interceptor system required 318 million bricks, 2.7×106 cubic metres (9.5×107 cu ft) of excavated earth and 670,000 cubic metres (24,000,000 cu ft) of concrete. [5] The innovative use of Portland cement strengthened the tunnels, which were in good order 150 years later. [6]
Gravity allows the sewage to flow eastwards, but in places such as Chelsea, Deptford and Abbey Mills, pumping stations were built to raise the water and provide sufficient flow. Many sewers north of the Thames feed into the Northern Outfall Sewer, which transports sewage to Beckton Sewage Treatment Works. South of the river, the Southern Outfall Sewer extends to a similar facility at Crossness. Smaller sewage treatment plants also serve areas further away from central London, such as at Mogden and Edmonton.
During the 20th century, major improvements were made to the sewerage system and to the sewage treatment provision to substantially reduce pollution of the Thames Estuary and the North Sea. The sewage works, from west to east, discharging into the tidal Thames in 1950-53 were: [7]
| Sewage works | Miles from London Bridge | Flow, million gallons per day |
|---|---|---|
| Ham | 17.3 above | 0.15 |
| Mogden | 15.0 | 83.2 |
| Richmond | 12.1 | 5.7 |
| Acton | 9.8 | 3.1 |
| Beckton | 11.4 below | 190.0 |
| East Ham | 11.7 | 4.5 |
| Crossness | 13.6 | 96.5 |
| Dagenham | 15.1 | 8.8 |
| West Kent | 19.4 | 22.6 |
| Stone | 20.9 | 0.3 |
| Swanscombe | 22.2 | 0.2 |
| Northfleet | 24.8 | 0.6 |
| Tilbury | 27.0 | 2.8 |
| Gravesend | 27.8 | 1.2 |
| Stanford-le-Hope | 32.1 | 0.4 |
| Corringham | 35.8 | 0.15 |
| Nevendon | 35.8 | 0.0 |
| Pitsea | 35.8 | 0.15 |
| Canvey Island | 37.1 | 0.15 |
| South Benfleet | 40.0 | 0.25 |
| Leigh-on-Sea | 40.0 | 0.45 |
| Southend-on-Sea | 44.6 | 6.6 |
The original system was designed to cope with 6.5 mm (1/4") per hour of rainfall within the catchment area, and supported a smaller population than today's. London's growth has put pressure on the capacity of the sewerage system. During storms, for example, high levels of rainfall (in excess of 6 mm per hour) in a short period of time can overwhelm the system. Sewers and treatment works are unable to cope with the large volumes of rainwater entering the system. Rainwater mixes with sewage in combined sewers and excess mixed water is discharged into the Thames. If this does not happen quickly enough, localised flooding occurs (surcharge). Such sanitary sewer overflow can mean streets becoming flooded with a mixture of water and sewage, causing a health risk.
In redeveloping the Isle of Dogs and Royal Docks areas of east London during the late 1980s and early 1990s, the London Docklands Development Corporation invested in major new drainage infrastructure to manage future sewage and surface water run-off from proposed developments. Consulting engineer Sir William Halcrow & Partners designed a system of large diameter tunnels served by new pumping stations. In the Royal Docks, approximately 16 miles (25 km) of foul and surface water drains were built, plus pumping stations at Tidal Basin (designed by Richard Rogers Partnership) and North Woolwich (architect: Nicholas Grimshaw). [8] The Isle of Dogs drainage network is served by a stormwater pumping station situated in Stewart Street, designed by John Outram Associates. [9]
Increasing the carrying capacity of London's sewerage system has been debated for some years. The new 'Thames Tideway' scheme includes a wide diameter storage-and-transfer tunnel (internal diameters of 7.2 m and 9 m have been suggested), 22 miles (35 km) long, underneath the riverbed of the Thames between Hammersmith in the west and Beckton/Crossness in the east. [10] The cost of this megaproject is £4.9 billion, [10] and it is due to be completed in 2024. [11]
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Subterranean London refers to a number of subterranean structures that lie beneath London. The city has been occupied by humans for two millennia. Over time, the capital has acquired a vast number of these structures and spaces, often as a result of war and conflict.
Sir Joseph William Bazalgette CB was a 19th-century English civil engineer. As chief engineer of London's Metropolitan Board of Works, his major achievement was the creation of a sewerage system for central London which was instrumental in relieving the city of cholera epidemics, while beginning to clean the River Thames. He was also the designer of Hammersmith Bridge.
The Thames Embankment is a work of 19th-century civil engineering that reclaimed marshy land next to the River Thames in central London. It consists of the Victoria Embankment and Chelsea Embankment.
Beckton is a suburb in east London, England, located 8 miles (12.9 km) east of Charing Cross and part of the London Borough of Newham. Adjacent to the River Thames, the area consisted of unpopulated marshland known as the East Ham Levels in the parishes of Barking, East Ham, West Ham and Woolwich. The development of major industrial infrastructure in the 19th century to support the growing metropolis of London caused an increase in population with housing built in the area for workers of the Beckton Gas Works and Beckton Sewage Treatment Works. The area has a convoluted local government history and has formed part of Greater London since 1965. Between 1981 and 1995 it was within the London Docklands Development Corporation area, which caused the population to increase as new homes were built and the Docklands Light Railway was constructed.
Abbey Mills Pumping Station is a sewage pumping station in Mill Meads, East London, operated by Thames Water. The pumping station lifts sewage from the London sewerage system into the Northern Outfall Sewer and the Lee Tunnel, which both run to Beckton Sewage Treatment Works.
The Northern Outfall Sewer (NOS) is a major gravity sewer which runs from Wick Lane in Hackney to Beckton sewage treatment works in east London; most of it was designed by Joseph Bazalgette after an outbreak of cholera in 1853 and the "Great Stink" of 1858.
The Southern Outfall Sewer is a major sewer taking sewage from the southern area of central London to Crossness in south-east London. Flows from three interceptory sewers combine at a pumping station in Deptford and then run under Greenwich, Woolwich, Plumstead and across Erith marshes. The Outfall Sewer was designed by Joseph Bazalgette after an outbreak of cholera in 1853 and "The Big Stink" of 1858. Work started on the sewer in 1860 and it was finally opened on 4 April 1865 by H.R.H. the Prince of Wales.
The Thames Tideway Tunnel is a 25 km (16 mi) combined sewer under construction, running mostly under the tidal section (estuary) of the River Thames across Inner London to capture, store and convey almost all the raw sewage and rainwater that currently overflows into the estuary. These events occur when rainfall volumes exceed the capacity of Bazalgette's and other engineers' London sewerage system. The tunnelling phase of the project was completed in April 2022.
The Great Stink was an event in Central London during July and August 1858 in which the hot weather exacerbated the smell of untreated human waste and industrial effluent that was present on the banks of the River Thames. The problem had been mounting for some years, with an ageing and inadequate sewer system that emptied directly into the Thames. The miasma from the effluent was thought to transmit contagious diseases, and three outbreaks of cholera before the Great Stink were blamed on the ongoing problems with the river.
Crossness is a location in the London Borough of Bexley, close to the southern bank of the River Thames, to the east of Thamesmead, west of Belvedere and north-west of Erith. The place takes its name from Cross Ness, a specific promontory on the southern bank of the River Thames. In maritime terms, the tip of Cross Ness, in the past referred to as 'Leather Bottle Point', marks the boundary between Barking Reach and Halfway Reach. An unmanned lighthouse on Crossness is a navigational aid to shipping.
Thames Water Utilities Ltd, known as Thames Water, is a large private utility company responsible for the water supply and waste water treatment in most of Greater London, Luton, the Thames Valley, Surrey, Gloucestershire, north Wiltshire, far west Kent, and some other parts of England; it has a considerable local monopoly.
The Crossness Pumping Station is a former sewage pumping station designed by the Metropolitan Board of Works's chief engineer Sir Joseph Bazalgette and architect Charles Henry Driver. It is located at Crossness Sewage Treatment Works, at the eastern end of the Southern Outfall Sewer and the Ridgeway path in the London Borough of Bexley. Constructed between 1859 and 1865 by William Webster, as part of Bazalgette's redevelopment of the London sewerage system, it features spectacular ornamental cast ironwork, that Nikolaus Pevsner described as "a masterpiece of engineering – a Victorian cathedral of ironwork".
The Tideway is a part of the River Thames in England which is subject to tides. This stretch of water is downstream from Teddington Lock. The Tideway comprises the upper Thames Estuary including the Pool of London.
The Lee Tunnel, also known as the Stratford to East Ham deep tunnel, is a paradigm overflow sewer in East London for storage and conveyance of foul sewage mixed with rainwater. It was built as part of the Thames Tideway Scheme and runs from Abbey Mills Pumping Station down to pumps and storage tanks at Jenkins Lane, Beckton Sewage Treatment Works. It is wholly under the London Borough of Newham.
Mogden Sewage Treatment Works is a sewage treatment plant in the Ivybridge section of Isleworth, West London, formerly known as Mogden. Built in 1931–36 by Middlesex County Council and now operated by Thames Water, it is the third largest sewage works in the United Kingdom. It treats the waste water from about 1.9 million people served by three main sewers serving more than the northwest quarter of Outer London and two further main sewers from the south and south-west. The plant has been extended and is constantly being upgraded with new process, most recently in OfWat Amp6 by the Costain Atkins Joint venture who delivered 6MW of Combined Heat and Power (CHP) generation, New process air blowers for Batteries A & B and six gravity sludge thickening streams. The site covers 55 hectares.
The Bondi Ocean Outfall Sewer is a heritage-listed sewerage infrastructure at Blair Street, North Bondi, Sydney, Australia. The sewer line commences at the intersection of Oxford Street and College Street in Darlinghurst and then travels in a more-or-less easterly direction for 6.1 kilometres (3.8 mi) passing through a number of suburbs until it reaches Blair Street in North Bondi. It was designed and built by the Public Works Department between 1880 and 1889. It is also known as BOOS (Bondi Ocean Outfall Sewer) and Main Northern Ocean Outfall Sewer. The property is owned by Sydney Water.
Greenwich Pumping Station, known until circa 1986 as Deptford Pumping Station, is a sewage pumping station in the London Borough of Greenwich built in 1865 to the east of Deptford Creek. It is part of the London sewerage system devised by Sir Joseph Bazalgette in the mid 19th century. Today operated by Thames Water, it is located on the western side of Norman Road, approximately 0.5 km (0.31 mi) south west of Greenwich town centre, on the eastern bank of Deptford Creek, around 0.5 km (0.31 mi) south of its confluence with the River Thames.
The Long Reach sewage treatment works is located in Dartford, Kent adjacent to the River Thames. It treats the sewage from a population of 837,000 in a catchment area of 518 km2 (200 sq mi) in south and south east London and west Kent. The treatment capacity of the works is 346 million litres per day (Ml/d).
