Excavation has commenced on the main shaft, whose floor will be the starting point for two tunnel boring machines (TBMs) to grind their way westward and eastward beneath the River Thames.
Behind the walls of the acoustic shed at the Kirtling Street site, excavation has started on the main shaft. The floor of this shaft, 60m below ground, will be the starting point for the tunnel boring machines (TBMs) which will tunnel in two directions to meet both the east and west sections of the Thames Tideway Tunnel project. Construction of this shaft, with a diameter of 32m, is a huge undertaking. Initially, three excavators will dig to a depth of 3m, a little more than the height of a room in an average house, before the team installs a capping beam, a reinforcing concrete and steel ‘border’ around the excavation to keep it stable. Once this is done, the excavators will work around the clock towards the 60m launch depth.
In the acoustic shed, the team is currently instating two gantry cranes, which will extract spoil from the shaft construction as it gets deeper. Each crane will be fitted with a custom made skip which can hold 12m3 of excavated material, making extraction much more efficient.
Naturally, this activity will produce a lot of spoil. As part of the team’s commitment to reducing their carbon footprint and road movements, all of the excavated material will be taken from site on river barges, with the largest of these having a capacity of 1,500tn.
“This is a significant milestone towards tunnelling. There is a great deal of work ahead and I am encouraged by our momentum. My congratulations to our teams on the progress made so far. It is exciting to see such a critical part of this project advance further every day”
The Thames Tideway Tunnel is a major new sewer that will help tackle the problem of overflows from the London’s Victorian sewers (millions of tonnes of raw sewage discharge into the River Thames) and will protect the river from increasing pollution for at least the next 100 years. Ferrovial Agroman is delivering the central section of the tunnel, alongside JV partner Laing O’Rourke.