Location: Māngere to Grey Lynn
What it’s all about?
In older parts of central Auckland, wastewater and stormwater flow into a combined network of pipes. When it rains heavily, stormwater can overwhelm these pipes. Unfortunately, this means that wastewater overflows with stormwater into our creeks and streams.
We want everyone to be able to enjoy clean waterways and open spaces, so we’re building a $1.2 billion wastewater tunnel across central Auckland called the Central Interceptor (CI). We also have other projects in the western isthmus, such as separating the stormwater and wastewater pipes. Together, the Central Interceptor and our western isthmus strategy will significantly reduce wastewater overflows in the area.
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.
To learn more about the Central Interceptor project, click here or the button below.