« Beijing - More Information
Calcutta »

London - Sewage System

Worlds Biggest Cities need a

History

In the early 19th century the was practically an open sewer, with disastrous consequences for public health in , including numerous cholera epidemics. Proposals to modernise the system had been put forward in 1856, but were shelved due to lack of funds. However, after The Great Stink of 1858, Parliament realised the urgency of the problem and resolved to create a modern system.

Joseph Bazalgette, a civil engineer and Chief Engineer of the Metropolitan Board of Works, was given responsibility for the work. He designed an extensive underground system that diverted waste to the Thames Estuary, downstream of the main centre of population. Six main interceptory , totalling almost 100 miles (160 km) in length, were constructed, some incorporating stretches of ’s ‘lost’ rivers. Three of these were north of the river, the southernmost, low-level one being incorporated in the . The Embankment also allowed new roads to reduce traffic congestion, new public gardens, and the of the Underground.

The intercepting , constructed between 1859 and 1865, were fed by 450 miles (720 km) of main that, in turn, conveyed the contents of some 13,000 miles (21,000 km) of smaller local . Construction of the interceptor system required 318 million bricks, 880,000 cubic yards (670,000 m³) of concrete and mortar, and excavation of over 3.5 million tonnes of earth.

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. north of the Thames feed into the Sewer, which feeds into a major treatment works at Beckton. South of the river, the Southern Outfall Sewer extends to a similar facility at Crossness.

In the 20th century, major improvements were made to the system to reduce pollution of the Thames Estuary and the .

[edit] Modern development needs

Victorian pipes now comprise less than 1% of the total network in .

The original system was designed to cope with up to 6.5 mm (1/4”) of rainfall within the catchment area, and supported a smaller population than today’s. ’s growth has therefore put pressure on the capacity of the system. During storms, for example, high levels of rainfall (in excess of 6 mm) in a short period of time can overwhelm the system. and treatment works are unable to cope with the large volumes of rainwater entering the system. Rainwater mixes with sewage in combined 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.

Increasing the carrying capacity of ’s system has been debated for some years. Proposals for the ‘Thames Tideway’ include 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 in the west and Beckton/Crossness in the east,[1][2] but as the cost of such a megaproject is likely to be substantial (estimated at £1.7 billion in 2004), investment decisions have been slow to be forthcoming. As of March 2007 it has been announced by the Mayor of that the project will proceed with completion expected by 2020.[3]

Because design and construction of such a tunnel will take an estimated 15 years, a shorter-term (and slightly lower cost) interim solution has also been developed. This £1.6 billion scheme (2006 prices) involves two shorter tunnels (one taking storm water from to Battersea for treatment or storage, the other carrying water from Abbey Mills south to the river at Beckton) and improvements to associated treatment facilities.[4]

[edit] Literary or media references

* The system plays a large part in English writer Neil Gaiman’s 1996 novel Neverwhere.
* The system plays a part in English writer Michael Robotham’s 2005 novel Lost.
* It also featured as one of the Seven Wonders of the Industrial World in the BBC television series of the same name.
* Eleanor Updale’s Montmorency (Beginning with Montmorency: Liar Thief Gentleman?) novels are set against the backdrop of construction of the system.

Related Blogs

This entry was posted on Friday, October 10th, 2008 at 3:25 pm and is filed under UK. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

Leave a Reply