The latest phase of work on the London Power Tunnels was completed eight days ahead of schedule, it emerged this week.
Costain carried out the work under a £200M contract for National Grid, with Skanska as a construction partner.
Tunnel boring machine (TBM) Evelyn broke through in mid-August into a pre-prepared shaft at Wimbledon, south west London, completing a 3km-long drive from Wandsworth in four months.
“To date, in over 10.5km of 3m internal diameter tunnel constructed we have incurred only one minor lost time injury and have increased our productivity levels to being able to maintain a consistent 60-plus metres per day,” said Costain tunnelling agent Angus Mackenzie.
One of the main technical challenges on this drive was a curve in the tunnel alignment that had a tight 22.5m radius.
The milestone is the latest on the project that has been under way since 2011. The project will create 32km of tunnels to house a new generation of 400kV electricity cables.
Evelyn is now being dismantled and split into its principal component parts to be inspected and refurbished ahead of its next and final drive on this project – a 9km stretch from Wandsworth in south west London to Kensal Green in the north west.
This is the longest drive on the 3m internal diameter section of the project and passes under the Thames. Work on this section begins at the end of October and is due to be completed by the end of 2014.
Meanwhile TBM Cleopatra is working on a 13km tunnel from St John’s Wood in north west London to Hackney in the east. The contract is due to be complete by 2014, with the new cables due to be switched on by November 2018.