Auckland’s $1.2 billion Central Interceptor wastewater pipe faces cost blowout

Auckland’s Central Interceptor wastewater tunnel. Photo / Watercare

Auckland’s City Rail Link blew out in cost from $4.4b to $5.5b in March. Watercare’s $1.2b giant wastewater pipe between central Auckland and Māngere treatment plan looks set to follow suit tomorrow.

Watercare is tomorrow expected to announce a cost blowout for the $1.2 billion Central Interceptor - a 14.7km wastewater tunnel from central Auckland to the Māngere treatment plant.

The Watercare board today discussed ratifying a settlement for cost escalation of the project behind closed doors.

A spokesperson told the Herald it will have more information to share on the issue tomorrow.

Similarly, a spokesperson for Mayor Wayne Brown said he may be commenting on the issue tomorrow.

The $1.2b Central Interceptor, being built by Watercare and joint venture partners Ghella (Italy) and Abergeldie (Australia), will reduce overflows into central Auckland waterways, streams and beaches, and stop the wastewater being mixed with stormwater. The project will also upgrade an antiquated wastewater network and cater for growth over the next 100 years.

The tunnel, an immense 4.5m in diameter, is designed to hold a capacity of 226,000 cubic m - equivalent to 90 Olympic swimming pools - and control the flow rate into the Māngere wastewater treatment plant.

The Central Interceptor is due to be completed in 2026 rather than 2025 because of interruptions caused by the Covid-19 restrictions and challenges.

For many years, Watercare has stuck to the $1.2b cost for the giant tunnel.

The cost of the City Rail Link blew out from $4.4 billion to $5.5b in March this year.

In March this year, it was announced the city’s biggest project, the 3.4km City Rail Link between Britomart and Mt Eden stations, had blown out in cost from $4.4b to $5.5b.

Auckland Council and the Government are partners in the CRL, sharing the cost equally.

Council-owned Watercare is funding the Central Interceptor through water bills.

Bernard Orsman is an Auckland-based reporter who has been covering local government and transport since 1998. He joined the Herald in 1990 and worked in the parliamentary press gallery for six years.