The CRL is the largest single transport infrastructure project in New Zealand's history.
It has been a vision for Auckland since the 1920s.
Read the CRL Business Case
This 2015 document was Auckland Transport’s internal business case to facilitate the Gateway Review process prior to letting contracts for enabling works construction. It was not a joint business case with government.
Here we list the big milestones in 2018:
City Rail Link starts Britomart tunnel excavation
24 July 2018
CRL has started excavating the 14-metre-deep trench that will contain the project’s twin rail tunnels under Britomart Station and Lower Queen Street in downtown Auckland.
UNDERWAY: : CRL Chief Executive Sean Sweeney (right) oversees the start of excavation with DSBJV Project Director Dale Burtenshaw
The excavation follows two years of careful preparation work to protect Britomart Station’s historic Chief Post Office (CPO) building and support the ground before the trenching and tunnel construction begin.
CRL contractor Downer-Soletanche Bachy Joint Venture (DSBJV) will start by removing a five-metre layer of ground from Lower Queen Street. This will lower the ground level sufficiently to allow excavators to start digging under the CPO building.
A single 25-metre-wide trench will be excavated in Lower Queen Street and two 10-metre-wide trenches under the CPO (the two future CRL platforms will be located on the far sides of the station).
CRL tunnel box construction is expected to start at this location at the end of this year.
Customs St intersection tunnel excavation starting
02 July 2018
Tunnel excavation under the Customs Street intersection is expected to start this week.
This work will pave the way for construction of the City Rail Link (CRL) tunnel box section that will link the Albert Street trench with the tunnels being built under the Commercial Bay development.
Thanks to the concrete bridge deck constructed over the intersection about a year ago, traffic flow will be unaffected by the excavation occurring underneath. The spoil will be removed from the site using excavators and conveyors.
CRL contractor Connectus (the Downer-McConnell Dowell Joint Venture) will also be removing an old brick stormwater tunnel located under the intersection and replacing it with a temporary stormwater line that diverts water away from the location of the future CRL tunnels. The temporary line will be permanently diverted at a later date to connect with the Swanson Street line, created during the Albert Street stormwater realignment works last year.
Construction of the tunnel structure is expected to start in this area later this year and a full connection made between the two construction sites by autumn 2019.
Secant piling completed
23 May 2018
Another milestone bringing us closer to construction of the City Rail Link tunnels that will make Britomart a through station.
It’s the completion of secant piling which has been happening in Lower Queen Street outside the former Chief Post Office (Britomart).
The secant pile walls will connect the excavation under Britomart to the excavation at Precinct Properties’ Commercial Bay development on the other side of Lower Queen St, where CRL tunnel boxes are being constructed.
70 secant piles had to be installed.
Secant piling is construction of intersecting reinforced concrete piles. These piles lock together for strength and control any groundwater ingress into the tunnel excavation.
A 70 tonne piling rig was brought in for the drilling.
Start of middle wall of tunnel box
03 May 2018
The middle wall of the first 12 metres tunnel box in Albert Street is presently being poured by the Connectus team (McConnell Dowell and Downer). The outer walls were done on Tuesday.
The middle wall is not as wide as the outer walls with a width of 460mm (600mm for the outer wall). It is slightly taller with a height of 5 metres (4.6m for the outer wall). It requires less concrete with 28m3 of concrete or 6 concrete trucks instead of the 60m3 used for the outer walls.
The steel formworks’ weight is doubled for the middle wall with a weight of 20 tonnes. The roof is scheduled for the end of this month.
Albert St tunnel box milestone
01 May 2018
The CRL Connectus team (McConnell Dowell and Downer) is pouring the first 12 metres outer walls of the tunnel box in Albert Street.
The team is pouring two walls, the east and west wall – the middle one will be poured later in the week and the roof is scheduled for end of May. 60m3 of concrete is needed for the two walls - that comes in 15 concrete trucks.
The eastern and western wall are 600mm wide and 4.66 metres high each. The steel formworks weigh 10 tonnes for each outer wall.
CPO building load transfer
01 May 2018
We’re a step closer to be able to start tunnel excavations in the former Chief Post Office (CPO) building.
Those excavations will turn Britomart into a through tunnel.
Contract one of the CRL works involves Downer NZ and Soletanche Bachy (DSBJV) progressing the CRL work through and under Britomart Station and Queen Street to the former Downtown Shopping Centre site which is now Precinct Properties Commercial Bay development.
They've achieved a new milestone.
This was that the first area of the CPO building that has been load transferred onto one of the structural steel underpinning frames.
There are 12 frames.
Why this is significant is because once all the load transfers are completed, we can then start tunnel excavations safely.
The weight of the building is carried by its columns down into the building foundations.
Before excavation of the rail tunnels can commence, a number of these foundations need to be removed – so the associated weight of the building firstly has to be transferred onto the underpinning frames.
Each affected column is clamped by a steel collar which sits upon a steel beam located either side of the column. A hydraulic jack is located beneath each corner of the collar (four jacks in total per collar) and these jacks are used to exert a force on the underside of the collar equivalent to the building weight carried by the column.
Each underpinning frame consists of two collars and the two beams. The beams span between two rows of diaphragm walls which were installed earlier during the project and are fixed to the capping beams which sit upon the diaphragm walls. Each frame supports two CPO building columns and the weight carried by both columns are transferred concurrently onto the frame during the load transfer for that frame.
During load transfer, the force exerted by each jack is slowly increased by increasing the hydraulic pressure within the jack and it is closely monitored along with any ‘lift off’ (displacement) experienced by the column. When the jacks exert a maximum specified force (predetermined by calculating the weight of the building carried by each of the two columns) or the column experiences ‘lift off’, the load transfer is complete.
Following construction of the rail tunnels and the subsequent re-build of the CPO building foundations, the weight carried by each column will be transferred back into the building foundations and the underpinning structures will be removed.
All heritage values of the former CPO building have to be maintained - the project is working closely with the Heritage New Zealand.
In January 2017, the Queen Street entrances to the Britomart Transport Centre closed for three years so that the CRL tunnelling work underneath could be done.
Albert Street Tunnel Box Pour
01 March 2018
The construction of the Albert St tunnel box is going well. The first 12 metres of waterproofing has been completed for the first slab so reinforcing works have just started.
The first slab will be completed on Saturday and the first pour will begin on Monday. Two tonnes bundles have been individually lifted between the struts to the trench floor by contractor CRS Ltd. It takes 8 steel fixers 5 days to tie together one floor slab (12 metres). 20 Tonnes of steel are used for the first slab.
Sandrine finishes her work
31 January 2018
Sandrine, the bright red 90-tonne piling rig has finished working around the historic CPO (Britomart) building for contractor Downer Soletanche-Bachy JV and was returned to France.
With Sandrine's help, 64 diaphragm walls (or D-walls) were built by the construction workers. The wall panels form the structural support for the tunnels to be built in the building and also prevent water ingress.
Albert Street Trench Construction Starts
14 February 2018
In Albert Street, construction of the first tunnel box is starting.
It takes three days to install the first 12 metres of the waterproofing.
The first step of the works is to place a first layer on the wall and floor.
This material is called filter cloth. It will protect the waterproofing membrane from perforation by the concrete.
Once installed, the waterproofing membrane can be placed on top.
Meanwhile, bulk excavation of the cut-and-cover trench on Albert Street is continuing towards the Customs Street intersection.
Behind the excavation stage, the construction of the tunnel box is getting underway.
This means installing steel mesh and pin into the wall of the trench for temporary rock support.
This is followed by ‘shotcreting’: this means spray-concreting a smooth surface for the waterproofing membrane of the tunnel box. The shotcreting team is currently completing the first 44 metres section of wall.
The last preparation step is the ‘blinding layer’: pouring concrete on the floor of the trench to form a flat, smooth layer for the concrete slab that holds the tunnel rails. The first 44 metres of blinding is already complete.
The team will then start the construction of 29 sections of tunnel box, each 12 metres long.
The waterproofing membrane is installed on the floor and walls, steel reinforcement is fixed for the base slab, and formwork installed before finally pouring tunnel concrete.
Once about 60 metres of the tunnel box is constructed, the team can start backfilling.
These steps will be followed, stage after stage, for approximately 350 metres of tunnel.
In the second half of the year, the Albert Street trench excavation will be completed and connected to the Precinct Properties site on the corner of Customs and Lower Albert Streets.
The tunnel box construction will continue all year, following behind the excavation.
By mid-year, the Albert Street trench will start to be backfilled between Wyndham and Swanson Streets and the first portion of road reinstatement is expected to start at that location before the end of the year.
Last concrete pour for CPO D-walls
31 January 2018
Downer Soletanche JV workers have begun the final concrete pour for the 64th and final diaphragm wall (D-wall) in the CPO. The walls were required to support the CRL tunnel excavation under Britomart Station.
The D-walls not only provide soil retention and control groundwater ingress but support the weight of the historic building during tunnel construction. It will also mean the end of the work there for the big piling rig Sandrine.
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