The Northern Line Extension has taken a step forward as the first of two giant tunnel boring machines, Helen, began her 3.2km tunnelling journey to extend the line from Kennington to Battersea.
The two tunnel boring machines, Helen, and Amy were lowered 20 metres below ground in Battersea in February, since when they have been preparing for tunneling work to start.
Helen has now set off under south London to create the first of the underground tunnels that will extend the Charing Cross branch of the Northern line from Kennington to Battersea Power Station, via Nine Elms.
The second TBM, Amy will follow in around a month’s time.
As the 100 metre long tunnelling machines advance forward, nearly 20,000 precast concrete segments will be put in place to form rings to line the tunnels. A conveyor system will then take the spoil from the tunnels up to barges on the River Thames. More than 300,000 tonnes of earth will be excavated by Helen and Amy in this way before the spoil is taken by barge to Goshems Farm in East Tilbury, Essex where it will be used to create arable farmland.
Each machine is capable of tunnelling up to 30 metres a day with teams of around 50 people operating them. Tunnelling is expected to take around six months to complete.
The extension is targeted for completion in 2020.
By coincidence, the Lower Thames Crossing route, confirmed today, passes almost next to Goshem’s Farm in East Tilbury:
http://assets.highways.gov.uk/roads/road-projects/Lower+thames+crossing/PRA/red-line+boundary+map.pdf
Perhaps they can send the Thames tunnel excavations to central London!