Project milestone…
The final puzzle piece of Auckland’s Central Interceptor is now in place following the removal of the massive bulkhead that separated the two halves of the tunnel during construction of New Zealand’s largest wastewater project.
Watercare chief programme delivery officer Mark Crowle says the project demonstrates long-term infrastructure planning and investment to support Auckland’s growth while protecting waterways, the environment and the communities connected to them.
“The bulkhead removal was the last major construction milestone for the project before the 16.2km tunnel becomes fully operational. This is a once-in-a-generation project and seeing it so close to becoming fully operational is exciting not only for Watercare, but for Auckland.”
The bulkhead removal was carried out at the project’s May Road site in Mt Roskill.
The glass-reinforced plastic and steel bulkhead was installed in 2024 to seal off the southern half of the tunnel ahead of it going live in early 2025. The structure protected crews working in the northern section of the tunnel while construction continued.
The removal operation required weeks of detailed planning to ensure it could be completed safely. Specialist divers from New Zealand Divers and Salvage were engaged to provide the expertise and protective equipment needed for crews working in a live sewer environment.
“The success of this complex work relied on continuous monitoring, clear communication between all the teams involved and strict adherence to our safety plan,” says Watercare lead engineer Emmanuel Vaki.
Although the bulkhead was installed in the tunnel as a single piece, it was removed in sections and lifted out through a 70m-deep shaft at the May Road site.
The glass-reinforced plastic dome was the final section to be removed.
To complete the operation, a gantry was mounted on a small vehicle and driven into the tunnel to support the dome while the metal body of the bulkhead was removed. Once the dome was ready for removal, it was towed out on the gantry vehicle before being lifted out of the shaft by crane.
Following removal of the bulkhead, the crew repaired the tunnel liner where the structure had been bolted and sealed in place, successfully completing the works.
The Central Interceptor is New Zealand’s largest wastewater project and is designed to improve the health of waterways and beaches across Auckland’s central and western suburbs by reducing wet-weather overflows.
The 16.2km tunnel runs from Point Erin in Herne Bay to the Māngere Wastewater Treatment Plant and is now complete. The project also includes two link sewers designed to capture wastewater flows from Blockhouse Bay, Avondale, Mt Roskill and Mt Albert.
The southern half of the tunnel has been operating since the start of 2025 and, as of March 2026, is estimated to have prevented 450,000m³ of combined wastewater and stormwater from spilling into the environment.
The tunnel is due to become fully operational by late July.
Crowle says the project reflects Watercare’s commitment to delivering infrastructure that supports Auckland’s future growth while providing long-term environmental benefits.