Another CRL milestone- bulk excavation work is starting for the cut and cover rail tunnels under Albert Street.
The excavation involves digging 18 metres (about five storeys) at the deepest (southern) point, using long-reach excavators above ground and smaller machinery inside the reinforced trench.
This represents about 10% of the 3.45km length of the twin-tunnel underground rail link,
The tunnels will then be constructed with a cast concrete floor, walls and roof before the trench is backfilled.
The work will be undertaken progressively from Wyndham St at the southern end to Customs Street at the northern end.
Excavation at the southern end is expected to be completed by October this year and the northern end by the middle of next year.
Construction of the tunnel box is expected to start late this year and be completed by late 2018.
The trench will be backfilled as the tunnel box construction is completed.
CRL project director Chris Meale says the start of bulk excavation is another milestone for the project.
“This work marks a significant point in the construction process as we will start to see the tunnels taking shape,” he says.
Chris Meale says: “It will be exciting and challenging work from an engineering perspective, as we build rail tunnels below ground water level, while maintaining surface-level access to Albert St for foot and vehicle traffic.
“The bulk excavation is also providing employment opportunities. When work begins, about 50 people will be working on site. This is likely to increase to 80 by the end of the year once tunnel box construction and water-proofing works are underway, with many being workers employed by local sub-contractors.”
Cut and cover construction is being used at each end of the CRL tunnels – between Britomart Station and the future Aotea Station and, later, where it connects to the western line at Mt Eden.
Between Aotea and Mt Eden stations, the tunnels will be between 13 and 42 metres below ground and bored using a 7m diameter tunnel boring machine.
The contract for the stations and bored tunnels is expected to be awarded in 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.
This is an early concept of the sort of look Albert Street could have after CRL construction.