According to the New Zealand Transport Agency, Alice ceased tunnelling on Friday 20 February.
In order to begin the next stage of digging and finish construction of the tunnel, the lengthy tunnel boring machine (TBM) must undergo a complex turnaround operation within an extremely narrow space.
NZ Transport Agency Highway Manager Brett Gliddon said the turnaround is expected to take ten weeks.
“Alice will then be ready for her main drive south towards Owairaka to complete the second – northbound – motorway tunnel. Breakthrough at Owairaka is expected next spring,” he said.
Watch a time-lapse video of the Waterview Connection progress to date:
Alice completed excavation of the project’s first tunnel in September 2014, travelling 2.4 km north from Owairaka to Waterview.
The front section of the TBM, including the cutter head, was turned around before Christmas and has already excavated 270 m of the second tunnel with the aid of a temporary gantry.
But this temporary gantry now has to be removed with her two remaining gantries pulled from the first tunnel, turned 180 degrees inside the Northern Approach Trench (NAT), then reconnected to the cutter head.
An infographic detailing the complex turnaround process can be found here.
Mr Gliddon said a total of up to 50 m of machinery had to be turned around within the construction area’s narrow confines, leaving only centimetres to spare.
“Turning a TBM of this size has only been done a couple of times before and we expect there will be a world-wide audience watching the turnaround of the remaining gantries. We anticipate the operation to go smoothly,” he said.
The Waterview Connection project is planned to open to traffic in early 2017.