Customer: Auckland Council Healthy Waters Contract: Construct Only Location: Downtown, Ports of Auckland

Fast Facts A new pipeline was installed to increase capacity for future growth in the upper catchment zones outlined in the Auckland Unitary Plan. Use of a three-metre diameter micro-Tunnel Boring Machine (m-TBM) to tunnel under Quay Street to a maximum depth of 18 metres. Installation of a 270 m inverted siphon pipeline. After completion, the pipeline will mitigate flood risk to the lower catchment area and surrounding properties.

The Ports of Auckland Outfall Upgrade Project, funded by Auckland’s Long Term Plan (LTP), has been in Auckland Council’s pipeline for several years, and we are pleased to construct this important infrastructure for downtown Auckland.

The design is an inverted siphon (U-bend shaped pipe). The horizontal section is three metres in diameter and approximately 270 metres long, installed within the East Coast Bays geological formation to avoid any risks associated with construction within reclaimed land.

The tunnel started at a temporary access shaft located within the Port of Auckland near the waterfront area connecting to a marine outfall. It extended under the operating port, rail-marshalling yards and Quay Street to a permanent drop shaft structure located between Quay Street and the North Island Main Trunk Rail Line.  The tunnelling phase was efficiently managed throughout the Covid-19 pandemic and weather events, including the Auckland Anniversary Weekend flooding and Cyclone Gabrielle.

This new stormwater culvert will increase the network’s capacity and improve the resilience of Auckland’s downtown infrastructure. The improved network will also mitigate flood risk for properties in the downtown area, including Britomart train station.

The next phase of the project involves repairs to the existing culvert so both systems can operate in parallel. Investigations have been completed and repairs are expected to start this February 2024.

This stormwater outfall upgrade draws on McConnell Dowell’s extensive track record in marine outfall construction using trenchless methodologies.

Work on this project includes:

• Service relocation works
• Piling works for both the outlet and inlet shafts
• Excavation works for both shafts
• Tunnelling under Quay Street to a maximum depth of 20 metres
• Chamber and outfall construction
• Culvert strengthening
• Investigations and repairs of the existing culvert

Check out the video below of the completion of tunnelling.