Watercare's $1.66 billion Central Interceptor is New Zealand's largest wastewater infrastructure project and is now fully operational. The 16.2 km tunnel, together with its intersecting link sewers, runs beneath Auckland city and the Manukau Harbour, providing a transformative solution for managing wastewater and stormwater flows across the region.
The project was constructed between 2019 and 2026 and is expected to dramatically reduce wet-weather overflows, improve the health of Auckland's waterways and beaches, increase network resilience and support future growth.
The southern section of the tunnel was commissioned in early 2025, with the northern section becoming operational in July 2026, marking the completion of this landmark infrastructure project.
AWMA’s Role in the Central Interceptor Project
AWMA was engaged by the head contractor, the Ghella Abergeldie Joint Venture (GAJV), on behalf of Watercare, to deliver engineered water control solutions for this complex system of shafts, chambers, and pump stations.
AWMA's scope of works included:
- Hydraulically actuated penstocks
- Electrically actuated penstocks
- Stop logs and stop plates
- Flap gates
- Hydraulic control systems (HPUs and pipework)
All gates are custom-manufactured from Duplex 2205 and 2507 stainless steel, delivering the strength and corrosion resistance required for long-term performance in a challenging wastewater environment.
Project outcomes
Throughout the delivery of the Central Interceptor, AWMA supplied and commissioned critical water-control infrastructure across several key sites, including:
- Keith Hay Park – Hydraulic systems, including HPUs in the plant room and gate assemblies within underground chambers.
- Māngere Pump Station – Two of the largest stop log systems ever manufactured by AWMA.
- PS23, Haycock Avenue & Māngere Treatment Plant – Gate systems installed, commissioned and fully operational.
With the completion of the Central Interceptor in 2026, AWMA's infrastructure is now supporting the long-term operation of one of New Zealand's most significant environmental and engineering projects.
Project Snapshot
- Length: 16.2 km main tunnel plus 4.3 km of link sewers
- Internal diameter: 4.5 m
- Depth: 15 m – 110 m below ground
- 17 construction sites, including 19 shafts
- Budget: NZ$1.66 billion
- Capacity: 250,000 m³ (99 Olympic swimming pools)
- Completion: Complete and Fully Operational (July 2026)
Delivering Long-Term Performance
