Auckland, New Zealand

The City Rail Link is the largest infrastructure project ever to be undertaken in New Zealand. The CRL is a 3.45km twin-tunnel underground rail link up to 42 metres below the city centre, transforming the downtown Britomart Transport Centre into a two-way through-station that better connects the Auckland rail network. Once completed, Britomart will no longer be a “dead end” station. The CRL is jointly funded by the Government and Auckland Council. The project‘s total cost will be within a funding envelope of $3.4b. CRL is due for completion in 2023.

Photo courtesy of cityraillink.co.nz

Project Requirements

  • The twin concrete tunnels needed to be built watertight to house a yet to be built rail loop.
  • The cut and cover construction meant a Tunnel Boring Machine would not be used for the initial phases.
  • The importance of the waterproofing support was considered very early in the design process. This required the Sika team to review hundreds of drawings in draft and from there develop fully compatible systems.


Sika was invited to pitch for design, support and supply of waterproofing systems for all enabling works of the C1, C2 and Commercial Bay stages. During the proposal development we faced many challenging situations including:

  • Sections of tunnel below sea level, as well as intersecting an underground water flow-path.
  • Construction methods already designed - we needed to offer a compatible fit.
  • Construction sequences requiring the connection of sections at different phases.
  • Detailing of complex connections and building in redundancies.
  •  Ensuring relevant supplier experience and local team support.
  • Comprehensive solutions that showed complete understanding of the project as a whole and the Stakeholder’s expectations

Products Used

Icosit® KC-340
Sika® WaterBars
Sika® WaterStop
Sika® Plan
SikaProof® A
SikaProof® P

Project Participants

Main Contractor
C1: Downer NZ & Soletanche Bachy
C2: Connectus

Auckland Transport