Keeping the Thames Clean Today

Written by Chad Hansen

With such an illustrious history, one might question the impact London’s expanding infrastructure and growing population continues to have on the River Thames today, and how this expansion will affect the river in the future. A constantly growing metropolis is limited by the size, quality and capability of its infrastructure. Two of Thames Water’s key aims are “ to provide sufficient capacity in sewers and treatment plants to meet the demand for wastewater services and to meet the necessary environmental standards” (Thames Water Website).

In Victorian times, the sewer systems were engineered to overflow in to the river during extreme weather conditions, in order to protect houses and streets from flooding. Joseph Bazalgette’s system was designed for 3 million people. Today, there are nearly 8 million people living in London. Due to the increase in population, and the effect that the emergence of concrete has on natural drainage, the sewers are overflowing in to the Thames once a week, on average. “Around 39 million tonnes of untreated sewage is discharged annually and as little as 2mm of rainfall can trigger a discharge” (Thames Water Website). In order to combat this phenomenon and improve the water quality of the river, Thames Water is planning the construction of the Lee Tunnel and Thames Tunnel, in addition to upgrading all five major sewage treatment works on the tidal River Thames.


The Lee Tunnel will be the deepest in London’s history, at eighty metres. At four miles, the tunnel will run under the Borough of Newham, from Abbey Mills Pumping Station to Beckton Sewage Treatment Works. The Lee tunnel will prevent 16 million tonnes of sewage and from spilling in to the River Lee each year at London’s largest single combined sewer overflow. Construction began in 2010 and the main tunneling work is due to start in January 2012. It will take just under two years to complete.

The Thames Tunnel is the largest and most challenging of Thames Water’s plan to reduce sewage discharge in to the River Thames. The 34 most polluting combined sewer overflows discharge in to the Thames once a week. Today, over 39 million tonnes of untreated sewage empty in to the river annually. Thames Water is attempting to intercept or control these CSOs, which will drastically limit this figure. If the issue was not addressed, this number would increase to seventy million tonnes in the next ten years. At seventy-five metres, the Thames Tunnel is five metres shallower than the Lee Tunnel, however it will be sixteen miles longer, and as wide and as tall as three London double-decker buses. The tunnel is planned to connect to the thirty-four most polluting sewer overflows, as identified by the Environment Agency (Thames Water Website).

The five sewage treatment facilities that Thames Water plans to upgrade are Mogden, Beckton, Crossness, Riverside and Long Reach. These five treatment works service most of London. Considering each of these facilities is the size of a small town, this is an extraordinary, as well as costly, undertaking. Thames Water is investing £675 million on sewage works upgrades, £636m on the Lee Tunnel and £4.1b pounds on the Thames Tunnel. These schemes will reduce the amount of untreated sewage entering the River Thames by around 90 per cent, and allow the river to flourish biologically as well as improve the experience of many people who use the river for recreation and leisure purposes.