Central Interceptor Main Works

Auckland, New Zeland

The Central Interceptor is a wastewater tunnel that will run between Grey Lynn and the Mangere Wastewater Treatment Plant. The tunnel will run underground at a depth of between 15 and 110 metres. It will cross the Manukau Harbour at about 15 metres below the seabed. Along the route it will connect to the existing wastewater network, which will divert flows and overflows into the tunnel.

The Works include a 14.7km long main tunnel excavated with a 5.45 m diameter Earth Presssure Balanced Tunnel Boring Machine (EPB TBM)  and two underground links of overall 4.3km excavated with two pipe-jacking machines, of ca 3m diameter each. The line will encounter 16 shafts reaching up to 80 meters depths, as well as numerous connecting sewers, chambers, control facilities and air treatment facilities.

The new sewer line is expected to reduce wastewater overflows in the central city by 80 per cent, improving water quality at some of the city's beaches, and to provide capacity in the wastewater network for future growth and development on the Auckland Isthmus for the next 50 years and beyond.