City Rail Link C2 – Enabling Works Contract

NZ
Auckland Transport
2015 - 2016

Abergeldie, through the acquisition of Harker Underground, were engaged as part of the Connectus Joint Venture to deliver the enabling works for Auckland’s inaugural underground rail link for Auckland Transport under the City Rail Link Contract 2. 

The project involved pipe jacking a new stormwater conduit from Swanson to Wellesley Street, strengthening the Orakei main sewer, and conducting cut-and-cover tunnels along Albert Street from Customs Street to Wyndham Street. 

Scope of works

The works included:

  • Installation of a 516m, 2m Ø stormwater pipeline using a Tunnel Boring Machine (TBM) and traditional pipe jack techniques, replacing the existing Albert Street stormwater line between Wellesley and Swanson Streets. This involved constructing an 18m-deep pipe jacking shaft at Victoria Street and reception shafts at Swanson and Wellesley Streets to facilitate TBM removal and connection to existing networks.
  • Strengthening 40m of the Orakei Main Sewer beneath Victoria Street. 
  • Construction of 350m of twin cut-and-cover tunnels along Albert Street, spanning from Custom to Wyndham Streets. 
  • Relocation of existing utility services. 
  • Implementation of extensive traffic management measures due to the CBD location of worksites. 
  • Excavation of a tunnel box to maintain continuous two-way traffic flow at the Customs and Albert Street intersection during the main tunnel construction. 
  • Construction of four integrated 2.2m deep concrete decks to support traffic overhead while safely excavating rail tunnels underneath. 

Complexity working in Auckland’s CBD

The City Rail Link C2 Enabling Works contract presented a highly complex and prominent project in Auckland’s CBD, involving the diversion of live stormwater and sewer lines to an 18m underground depth. The tunnelling scope required meticulous 3D modelling and planning to ensure the works were carried out successfully. 

The project team employed cutting-edge piling technology with the 170T SR100 double-rotary cased continuous flight auger rig, a first for New Zealand. Standing at nine stories high, it effectively preserved adjacent ground integrity and minimised vibration effects throughout the piling operation using CCFA technology.

An automated real-time survey monitoring system was implemented, providing detailed records of all project impacts, and helping to mitigate stakeholder concerns. Concurrently, automatic real-time monitoring of groundwater in the project vicinity also occurred.

All components of the C2 works involved significant excavations within a densely populated urban area. This created a complex interface between construction sites, urban streets, and local stakeholders. Innovative techniques were developed to remove, treat, and dispose of groundwater. Complex arrangements of settlement tanks, silt busters, and flocking systems were implemented to manage environmental risks. This was then closely monitored by a dedicated environmental team.

To mitigate odour risks during works on the Orakei Main Sewer a deodorising system was developed and implemented within the Victoria Street shafts. Real-time live dust monitoring was also put in place to track dust and monitor construction techniques. 

All aspects of the works adhered to Mining and Tunneling regulations and WorkSafe’s guidelines. 


Enabling the new railway line to double rail capacity

The works carried out have helped to facilitate a new railway line that better connects Auckland’s rail network and will double rail capacity.