Bulkhead removal final puzzle piece for Central Interceptor

The final puzzle piece of the Central Interceptor tunnel is 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 is a prime example of Watercare’s investment in long-term infrastructure and planning to support a growing Auckland for generations to come, while protecting the health of the water, environment and 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 Mount 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, to protect the crew working in the northern part of the tunnel.

The removal operation took weeks of meticulous planning to make sure it could be done safely, with specialist divers New Zealand Divers and Salvage engaged to provide expertise and protective equipment needed for the crew to work 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 one piece, its components were removed separately and lifted out of a 70-metre-deep shaft at the May Road site, with the glass-reinforced plastic “dome” the final piece to come out.

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 a crane.

The crew repaired the liner of the tunnel where the bulkhead had been bolted and sealed in place, successfully completing the works.