Network Rail and contractor J. Murphy & Sons are enlarging one of the 19th century bores to accomodate a double-track railway and overhead line equipment.
Electrification of the route between Manchester and Bolton has involved filling the up-tunnel with foam concrete and re-boring it. Meanwhile, the down-tunnel was strengthened to allow single-line working while the tunnelling was taking place.
It hasn’t been entirely straightforward for the project teams. Loose sands , which hadn’t been picked up by initial ground investigations, ran into the excavated area early in the boring programme, setting back the original completion date.
Murphy’s project manager Mick Boyle said: “Breaking through with the TBM yesterday is a big step to ensuring that the tunnel is secured for many decades of providing a more efficient railway for Network Rail and passengers.
“This has been an exciting project to work on and demonstrates the skills of our team who have worked very hard to ensure that we have reached this milestone.”