Here are the latest time-lapse videos - inside and outside the CPO/ Britomart and along Albert Street.
Outside the CPO/ Britomart
Sandrine, a 90-tonne compact hydrofraise piling rig, is digging 15 to 20-metre-deep diaphragm wall (or D-wall) panels that will form the structural support for the CRL tunnels at the CPO / Britomart building.
A D-wall is a continuous wall constructed in the ground, typically to form an underground barrier or structure.
The purpose of the walls is to allow the rail tunnels to be constructed by supporting the existing foundations of the Chief Post Office (the underpinning structure will be supported from the D-walls), to provide ground retention during excavation for the rail tunnels and to prevent groundwater ingress into the excavations.
Inside the historic former Chief Post Office building in Lower Queen Street
Contractors Downer NZ and Soletanche Bachy (DSBJV) are preparing for the cut and cover works to build the CRL twin tunnels from the outer platforms at Britomart.
Recent work on the Britomart Transport Centre floor, where you used to head in to get the train, includes deconstruction and demolition work and removal of the floor.
Along Albert Street
The bulk excavation, taking place in Albert Street, is proving challenging work for CRL engineers. They must construct rail tunnels below groundwater level while maintaining surface-level access to Albert Street for foot and vehicle traffic.
The excavation involves digging 18 metres at the deepest point, using long-reach excavators above ground and smaller machinery inside the reinforced trench. The tunnels will then be constructed with a cast concrete floor, walls and roof before the trench is backfilled.
It represents about 10% of the 3.45km length of the twin-tunnel underground rail link. The work is being undertaken progressively from Wyndham St at the southern end to Customs St at the northern end.
Excavation at the southern end is expected to be complete by October and the northern by the middle of next year. Construction of the tunnel box is expected to start late this year and be completed by late 2018. By spring 2019, this section of Albert St will be reinstated with a new road surface, bus lanes, widened footpaths and street furniture.