The Tunnel

Our 25km tunnel will intercept, store and ultimately transfer sewage waste away from the River Thames.

The tunnel is 7.2 metres diameter wide, the equivalent of three London double decker buses, and the two connection tunnels are 5 metres in diameter and two metres in diameter respectively – 5 metres being roughly the size of a London Underground tunnel.

At Acton in West London where we start the tunnel, we are at our shallowest, 31 metres deep. It then falls away at a rate of 1 metre every 790 metres. Falling to 66 metres when we reach Abbey Mills Pumping Station in East London.

Four giant tunnelling machines were used to excavate the main super sewer, each named after inspirational women with a connection to the local area.

Two smaller tunnelling machines were used to create connection tunnels in Greenwich and Wandsworth.

Watch how TBM Selina started her journey at Chambers Wharf:

TBM Selina is named after Dr Selina Fox, who founded the Bermondsey Medical Mission in 1904. The small clinic and eight-bed hospital provided medical and spiritual care to the most vulnerable women and children in the area and continues to this day as a local charity.

21 shafts were built across the project – some to launch tunnelling machines, most to channel sewage flows into the super sewer.

Watch how the shaft at Greenwich Pumping Station started excavation:

The super sewer has a storage capacity of 1.6m cubic metres, or around 600 Olympic-size swimming pools.

With the construction of the heavy engineering completed, the system commissioning phase has now started and will take away flows of polluting sewage into the tunnel to protect the river for the first time.