From transferring 14,000-tonne historic buildings to new foundations to avoiding volcanic lava flows, the Auckland City Rail Link (CRL) project has been one of the more challenging transport infrastructure projects in the Australian/New Zealand pipeline.
Similar to other jurisdictions however, Auckland has had a significant population increase. Since 2010, Auckland’s population has risen by 50 per cent.
“We were at a stage where the road network was unable to cope,” City Rail Link’s CEO, Dr. Sean Sweeney, said at AusRAIL PLUS 2019.
When a new station was built in 2003, it took until 2014 for the line to be electrified and new rollingstock provided. This resulted in the doubling of patronage numbers.
“That passenger growth has continued ever since and City Rail Link has an ever-increasing need for public transport.”
Construction towards the $4.4 billion project officially commenced in 2018 with preliminary works ongoing since 2016. Its scope consists of the construction of twin 3.5 km long double-track rail tunnels underneath Auckland’s city centre, between Britomart Transport Centre and Mount Eden Railway Station.
Two new underground stations will be constructed at Aotea and Karangahape. Britomart will be converted from a terminus station into a through station and Mount Eden Station will be completely rebuilt with four platforms to serve as an interchange between the new CRL line and the existing Western Line.Wider network improvements are also part of the project.
It is slated for completion by 2024.
“Similar to Sydney and Melbourne, we’ve got some form of a loop. The Western line and the Southern line converge at one railway station with the Eastern line, so all of Auckland’s rail traffic goes into the Britomart station and then basically stops there so that the trains get backed up, full or not,” Sweeney said.
“Essentially, what City Rail Link is seeking to do is make Britomart a through station and extend the line back up to the rail network so you can run trains in both directions. Then, by enabling longer, nine car trains, with longer platforms, we can triple the capacity of the rail network.”
This means increasing capacity from 14,000 pph to 54,000 pph into the CBD, allowing for a train every ten minutes in peak.
“By our calculations that’s the equivalent of sixteen lanes of traffic into the city centre in peak,” Sweeney said.
This will double the number of people within 30 minutes of NZ’s biggest employment hub, bringing with it significant commercial and residential opportunities around stations.
Though early works commenced in 2016, Sweeney explains that about ten years ago a forward-thinking Auckland mayor decided to start the project without funding from central government.
“This project had quite an unusual start. The mayor realised that to make Britomart a through station someone had to start building tunnels underneath the city, so Auckland council went out and started construction without central government support which was a very brave thing to do.
“They managed it with a whole range of contracts and multiple contracting types, which made it a little bit confusing but it was what they had to do to get going, and it’s gotten off with different forms of construction, bored tunnels, cut and cover tunnels, etc. There’s a really complex grade separation into existing railway lines.”
One of the challenges for the project is that Auckland is built on volcanoes, “some of which erupted as recently as 800 years ago, which is very recent geologically”.
“So, to try and avoid some of the recent lava flows we built an incredibly complex geological model. We used the information that was available to us to plot the safest route. We used this model to locate the top striations, so to avoid some of the most recent lava flows. That was a very complex investigation and we have made that model available to the bidders.”
Another challenge is the current size of the infrastructure pipeline across a number of sectors in Australia and New Zealand.
Over an eighteen-month period, Sweeney tracked the pipeline from $80 billion in September 2017 to more than double that in August 2018, and then $220 billion in February 2019.
“I’ve never encountered this extent of growth and the way that this complicates what we have to do and the effect it has on our market is a real stretch. Certainly, historically New Zealand has built very little in 20 years and so, even getting major international contractors to take us seriously and come and bid for us was a big piece of work.”
However, early works are now “pretty much completed” according to Sweeney.
Moving forward, the agency has wrapped up the outstanding works (highlighted in yellow) – including the remaining tunnels, stations and rail systems infrastructure, as well as the related wider network and tracks – into one contract, Contract 3, to be delivered by a ‘Grand Alliance’.
The alliance consists of: Downer, AECOM, Tonkin + Taylor, WSP Opus, Soletanche Bachy, and Vinci Construction.
In October 2019, the demolition of thirty empty buildings demolished near the Mt Eden railway station began. This will ensure space for the construction of the southern portal for the City Rail Link’s twin tunnels. The cleared site will be used as a staging area for a Tunnel Boring Machine and other machinery.
The first phase of this demolition is due to be completed in March 2020 , and is being managed by the alliance.