The company, which is working on the project along with Skanska, said it has reached eight days ahead of schedule.
On 15 August 2013, the tunnel boring machine (TBM) Evelyn broke through into a pre-prepared shaft at Wimbledon, southwest London, which represents completion of a 3km long drive from Wandsworth in just four months.
It completes the latest stage in the creation of 32km of tunnels being built to house a new generation of 400kV electricity cables under London.
Tunnelling agent Angus Mackenzie said, "This is certainly the safest and the quickest tunnelling contract I’ve ever worked on.
"To date, in over 10.5km of 3m internal diameter tunnel constructed we have incurred only one minor LTI (lost time injury) and have increased our productivity levels to being able to maintain a consistent 60-plus metres per day," Mackenzie added.
"One of the biggest technical challenges on this drive was a curve in the tunnel alignment that had a tight 22.5m radius. This gave us issues with the pit bottom as the drive shaft was centred on this curve but, using a combination of experience and new ideas, we were able to design around this."
Evelyn will now be dismantled and split up into principal component parts in order to inspect and refurbish ready for the next and final drive on the project.
The final part of the project is 9km from Wandsworth to Kensal Green in northwest London and will begin at the end of October 2013 and is slated to be complete by end of 2014.
