Central Interceptor

Sector

Water & Wastewater

Location

Point Erin, Herne Bay to Māngere Wastewater Treatment Plant, Auckland, Auckland

Started

2019

Completed

2026

The Central Interceptor is a 16.2 km wastewater tunnel under Auckland. It runs from Point Erin in Herne Bay, beneath the central suburbs and the Manukau Harbour, to the Māngere treatment plant. Its job is to catch the wastewater and stormwater that used to overflow into streams and beaches whenever it rained heavily. The tunnel is 4.5 m across and lies between 15 and 110 m underground. It can hold 299,000 m³, enough to store the surge from a storm until the treatment plant can take it. A 190 m tunnel boring machine named Hiwa-i-te-Rangi dug it. The project also needed 19 shafts, some up to 75 m deep, and 97% of the spoil was kept out of landfill. The southern half went live in early 2025, and the whole tunnel was running on 20 July 2026. At $1.66 billion, it is the country's largest investment in wastewater infrastructure.