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Diary of a contractor: Auckland's City Rail Link

The Connectus Joint Venture team is delivering Contract 2 for City Rail Link Limited. The City Rail Link (CRL) creates a 3.45 kilometre twin-tunnel rail link up to 42 metres below Auckland’s city centre. Contract 2 represents about 10 percent of this project and involves the construction of rail tunnels within the Albert Street road corridor from Customs Street West to Wyndham Street, together with a new stormwater line from Swanson Street to Wellesley Street, and a large number of underground utility works.

In the middle of Auckland city, Connectus – the McConnell Dowell and Downer joint venture – has come back on site after two weeks break over Christmas and New Year. The team has recharged its batteries and is ready to continue progress on the City Rail Link twin-tunnel underground rail link.
In 2018, the Connectus team will continue the bulk excavation of the cut and cover trench on Albert Street, towards the Customs Street intersection. Behind the excavation works, the team is now building the CRL tunnel box. The trench is approximately 300 metres long by 13 metres wide, of which 6.5 metres is covered by a construction deck. Excavation is due in mid-2018.

In 2017, the Connectus team reached numerous milestones for the project.


April: the team completed 362 piles 20 metres deep, using a Soilmec SR100 Cased Continuous Flight Auger (CCFA) piling rig. This forms the perimeter of the CRL tunnel box under Albert Street, following five months spent relocating gas, electricity, telecommunication, stormwater and wastewater utilities.
“Piling in the CBD brought a variety of challenges, including environmental, coordination and logistics of over-dimension deliveries, frequent traffic switches and the general operation of a 150 tonne piling rig adjacent to pedestrians and live traffic lanes. The works required the team to react quickly to challenges.” – Craig Langsford, Connectus site engineer

Top of the Albert Street trench.

July: the team started the bulk excavation on Albert Street, using a cut and cover method. The trench on Albert Street goes from Wyndham Street to Customs Street – about 10 percent of the City Rail Link.
“It is quite unique to be undertaking deep excavation works and have both pedestrian and vehicular traffic suspended overhead, and this is possible because of the design and methodology Connectus developed. It is fantastic to see members of the public stopping on the two viewing platforms we have installed and showing interest in the project.” – Hugh Robinson, Connectus construction manager

October: the Customs Street traffic deck was completed. The traffic deck constructed at the intersection of Customs and Albert Streets means the team can mine underneath while city traffic moves overhead.

November: the full 18-metre depth was reached at the southern end of Albert Street trench. The team also started removing the 100-year-old stormwater pipe sitting 18 metres deep at the southern end, and gets to the redundant pumping chamber in Customs Street at a depth of eight metres to its base. The team also installed the last of the 201 thick concrete slabs that form the construction and public traffic lanes along Albert Street. In total, the slabs weigh approximately 1339 tonnes.
“It’s a great achievement for the team and another milestone reached for the City Rail Link project. It took about seven months to complete the construction and public traffic deck, which included the pre-works, digging, removal of the top 1.5 metres of the road and protection of utility services.”Aaron Ghazal, Connectus site engineer 

By Christmas:  Albert Street was re-opened between Swanson and Customs Streets. Anyone driving down Albert Street on this section is currently suspended up to 16 metres in the air, while bulldozers, diggers and shotcrete workers continue to build the CRL underneath.
Connectus has now poured the first 44 metres of concrete for the tunnel box, beside the Auckland District Court and the Wyndham Street viewing platform. This first concrete pour is the “blinding layer” to form a flat and smooth layer for the next layer above it, which will be the waterproofing membrane. This will be followed by construction of concrete floor slabs for the first section of tunnel box.
December: marked the completion of major stormwater diversion works. A new stormwater main had to be constructed along the eastern side of Albert Street, between Swanson and Wellesley Streets. This was done by pipe-jacking (micro-tunnelling), replacing the existing line that ran along the centre of Albert Street, in the the path of the future CRL tunnels. A two-metre-wide tunnel boring machine (TBM), named ‘Valerie’ in honour of the strength of Olympian Valerie Adams, simultaneously excavated and installed a new stormwater pipe under Albert Street. The Orakei Main Sewer was also strengthened underneath the future Aotea Station.
Shaft sites on Swanson, Wellesley and Victoria Streets to either launch or receive the TBMs were finally all removed just before Christmas.
“The work around Victoria Street has proved very challenging logistically with very tight sites and difficult access points in a very busy CBD intersection. The new pipes are now operational and we’re happy to have handed the street back to the local businesses, which have been very patient throughout the construction phase.” – Thomas Jefferd, Connectus project engineer

This article was first published in the February 2017 issue of NZ Local Government Magazine.

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