City Rail Link, engineering, new zealand,

June 28, 2021

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City Rail Link New Zealand – 2020/2021 Project Update

It has been over two years since we last gave you an overview of the City Rail Link NZ project. We thought it was about time to update you on its progress.

To give you a quick recap, the City Rail Link project is currently the largest infrastructure project in New Zealand. It will completely transform the public transport network for Auckland’s residents.

The project consists of constructing a 3.45 km long twin-tunnel underground rail link up to 42 metres below the city centre. The double-track rail tunnel will run between Britomart Transport Centre (a dead-end station) and Mt Eden Railway Station.

Read our 2019 blog giving a more in-depth overview and background of the City Rail Link NZ project: Click here.

The Stations

On completion, the City Rail Link NZ Project Auckland will have two new underground stations and the redevelopment of a few existing stations Mt Eden and Britomart Station. Below is an overview of each.

1. Britomart train station

The Britomart station has been closed since Jan 2017, at the beginning of the City Rail Link project. This closure was necessary to create the twin rail tunnels 14m beneath the building. 600m of tunnelling now exist between Britomart and the lower end of Albert Street.

With significant works occurring directly under the top-rated heritage building, Chief Post Office (CPO) at Britomart station, there was no margin for error. To successfully transfer the CPO’s weight onto temporary foundations to keep the historic building protected during construction, was a complex engineering task.

2. Aotea train station

The Aotea station is a new 15m deep 300m long underground mid-town station near Wellesley and Victoria Streets and is expected to be NZ’s busiest station.

Pre-construction activities have already taken place along Wellesley and Victoria Streets, with various buildings being demolished to make space for the Aotea Station construction.

View the Aotea train station concept designs here.

3. Karangahape train station

The Karangahape station will be another new station for Auckland and is located in Mercury Lane. It will be the deepest of the City Rail Link NZ stations at 32m deep.

This new station will have two entrances and is expected to unlock additional high-density residential development.

View the Kanangahape train station concept designs here.

4. Mount Eden train station

The current Mount Eden station will be enlarged and re-developed, covering both the existing Kingsland to Grafton Line.

The Tunnels

The 3.45km twin-tunnels underground rail link includes tunnels up to 32m below the city centre streets.

Each end of the tunnels will be shallow enough to construct the tunnels using the cut and cover method. Cut and Cover tunnels are built by excavating from the surface and installing retaining walls to retain the soil and stop water from entering the site. Tunnels are then constructed inside the trench, and the completed structures backfilled.

The tunnelling route will typically follow the road network above it to minimise the amount of traffic affected by the project. Where the excavation of the tunnel is deeper, the tunnel boring machine (TBM) will be utilised. The City Rail Link NZ TBM is named after Māori rights activist Dame Whina Cooper and arrived in New Zealand from China in late 2020.

Tunnelling has begun from Mt Eden Station moving towards Karangahape Station and Aotea station. It will then be finishing its journey linking with the tunnels already dug at Britomart station.

From January to June 2021, the first tunnel will reach Beresford Square and consist of a total length of 278 metres of excavation with 23,000m3 of spoil removed and 2,700m3 of shotcrete sprayed onto the walls of the tunnel.

City Rail Link NZ Project Milestones

2020 Project Milestones

June 2020 – The first quick “blast” at the Mt Eden station construction site took place, and a ceremony was held to mark the start of construction for the Aotea Station.

September 2020 – The noise enclosure in Mercury Lane is nearly finished and will allow Link Alliance construction workers to work 24 hours a day.

October 2020 – The TBM has been manufactured and ready to depart the Chinese factory and head to Auckland. At the same time, the lower end of Albert Street has been restored and improved with the CRL tunnels underneath.

November 2020 – The CPO building has been restored and preparing to reopen. Ōtāhuhu Station improvements have been completed, including a new platform.

December 2020 – 5000 Aucklanders visited the TBM up close at the Mt Eden construction site. Mining also started at the Mt Eden tunnel portal to enable the launch of the TBM.

2021 Project Milestones

April 2021 – The Aotea Station construction moved underground, and the CPO reopened after being moved on to temporary foundations to protect the heritage-listed building.

07 May 2021 – The TBM is switched on, ready to bore at the Mt Eden site. Final checks were made before the TBM could start cutting into the soil.

27 May 2021 – Dame Whina Cooper TBM has started its journey below to excavate the City Rail Link tunnels.

22 June 2021 – Today, the City Rail Link NZ TBM has travelled 32m, installed 18 concrete rings, and removed 1700 tonnes of earth.

You can track the TBM’s journey in real-time here.

Fast Facts About the City Rail Link NZ

• It is the largest transport infrastructure project ever to be undertaken in Aotearoa, New Zealand.
• Will allow the rail network to at least double capacity to cope with future transport demands.
• The City Rail Link NZ is a 3.45km twin-tunnel underground rail link up to 32m below the city centre.
• Completion of the project is due in late 2024.
• It will extend the existing rail line underground through several key city stations.
• The Government and the Auckland Council jointly fund the City Rail Link Project NZ.
• The project is budgeted to cost NZD 4.419 billion.
• A single Alliance is delivering the main CRL works – the stations and tunnels. The successful bidder was the Link Alliance (Vinci Construction Grands Projets S.A.S., Downer NZ Ltd, Soletanche Bachy International NZ Limited, WSP Opus (NZ) Limited, AECOM New Zealand Limited and Tonkin + Taylor Limited).

Source: City Rail Link, visit their website here.

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