Work began on Monday on bulk excavation for the city rail link cut-&-cover rail tunnels under Albert St in downtown Auckland.
City Rail Link Ltd project director Chris Meale said it was a milestone for the project: “This work marks a significant point in the construction process as we will start to see the tunnels taking shape. It will be exciting & challenging work from an engineering perspective, as we build rail tunnels below groundwater level, while maintaining surface-level access to Albert St for foot & 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 & waterproofing works are underway, with many being workers employed by local sub-contractors.”
The excavation represents about 10% of the 3.45km length of the twin-tunnel underground rail link, and involves digging 18m (about 5 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 & roof before the trench is backfilled.
The work will be 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 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 & street furniture.
For those interested in watching the big dig, CRL & contractors the Connectus joint venture (McConnell Dowell & Downer) have provided viewing windows at the Wyndham St pedestrian crossings.
Cut-&-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 & Mt Eden stations, the tunnels will be between 13-42m below ground and bored using a 7m-diameter tunnel boring machine.
The city rail link is jointly funded by the Government & Auckland Council and is expected to be completed in 2023-24. Their joint venture company, City Rail Link Ltd, took over the project on 1 July.
Image above: Looking north along the CRL tunnel route on Albert St.
Attribution: Company release.