Tunnelling Support for Auckland’s City Rail Link

PDP supported multiple stages of the City Rail Link (CRL) – New Zealand’s largest transport infrastructure project – providing specialist groundwater expertise from feasibility through to consenting. The project includes twin 3.45 km tunnels running up to 42 metres beneath Auckland’s CBD, new underground stations, and connections to existing infrastructure.

Our work included the development of a conceptual hydrogeological model and detailed assessments of potential drawdown, inflow, and ground settlement effects. This involved both analytical and numerical modelling using 2D and 3D techniques to simulate groundwater behaviour across various tunnelling scenarios. These assessments formed a key part of the project’s Assessment of Environmental Effects (AEE), supporting resource consent applications.

We also provided expert witness services during the consenting phase and contributed to the design and management of a drilling programme, including installation of piezometers and aquifer testing. A 28-day constant-rate pumping test was carried out to evaluate aquifer characteristics, stormwater interaction, and water quality parameters. Throughout, our team supported stakeholder engagement and regulatory responses as the Suitably Qualified and Experienced Person (SQEP), ensuring the project’s complex groundwater risks were thoroughly addressed.