New Zealand’s largest infrastructure project has reached another important milestone.
Bulk excavation work for the City Rail Link (CRL) cut and cover rail tunnels under Albert Street in downtown Auckland has begun.
The excavation represents about 10 per cent of the 3.45km length of the twin-tunnel underground rail link.
It 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.
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 complete by October this year 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.
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.
“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 with about 50 people 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.
Jointly funded by the government and Auckland Council, the CRL is Auckland’s top transport priority and is expected to be completed in 2023/24.
