City Rail Link – C1 – Underpinning CPO Building

As part of the wider City Rail Link project, the C1 enabling works contract comprised the extension of the Britomart rail station and tunnels under the existing historic Central Post Office (CPO) Building using the cut & cover method without disruption to rail services or damage to the structure or surroundings. 

The scope of this project comprised: 

• 3155sq.m 600mm & 800mm thick diaphragm walls constructed in 6.5m headroom and confined access for retention and underpinning the building
• 58No. 1.4m diameter jet grout columns where the installation of a diaphragm wall was not possible due to the existing structure
• Construction of rail tunnels for the City Rail Link (CRL) project beneath the existing Central Post Office (CPO) “Britomart” building
• Developing a Reconstruction of CPO basement and ground floors, including the installation of underpinning structures to transfer the 14,000-ton 100-year-old CPO building from its original foundations onto new foundations.