New Zealand's largest bored wastewater tunnel
The Central Interceptor (CI) tunnel is 4.5 metres in diameter and will run for 14.7 kilometres from Grey Lynn under central Auckland and the Manukau Harbour to Māngere. The tunnel will lie between 15 and 110 metres below the surface. Along with two smaller link sewer tunnels we are building, the main CI tunnel will collect wastewater from the existing network and take it to the Māngere Wastewater Treatment Plant.
We’re using state-of-the-art tunnel boring machines (TBMs) from Germany to build the tunnel. It will slope at a gradient of 1:1000 so the wastewater can flow downhill to Māngere.
Above ground there are 16 construction sites. There, we are creating permanent access shafts and drop shafts along with control and overflow structures, and air treatment facilities for future operational use.
The project, which is the largest wastewater project in New Zealand's history, offers a number of key benefits.