Massive housing growth in northwest Auckland is coming with an $800 million bill for new and improved water services.

With 300,000 people expected to call the northwest home over the next 50 years, Watercare is starting work on a new watermain and wastewater pipeline project.

Thousands of new homes are already hooking up to water services at Hobsonville and Kumeu, but Watercare chief executive Raveen Jaduram says the new pipelines will boost capacity for future housing and commercial development over the next 30 years.

One project is the $538 million northern interceptor, a large wastewater pipe that will divert flows from northwest Auckland to the Rosedale wastewater treatment plant on the North Shore and manage growth in the area until 2070.


Sewage from the northwest now goes to the Mangere wastewater treatment plant.

The second project is a new $264 million watermain, running 33km from the west to a new reservoir completed at Albany in November last year. The current watermain from Titirangi to the North Shore, Whangaparaoa and Orewa, built between 1975 and 1985, cannot be maintained without disrupting local water supplies.

Last year, Watercare gained approval to install a smaller stage one northern interceptor wastewater pipeline for growth areas in Massey North, Whenuapai, Hobsonville, Kumeu, Huapai and Riverhead, which it will start building next year.

Watercare is applying this year for statutory approvals - largely in the road corridor, although some work will be needed on private property.

Said Mr Jaduram: "The northern interceptor and North Harbour pipelines will help enable growth in the fastest growing areas in New Zealand."

According to Auckland Council's medium growth project, the city's population is expected to increase by 700,000 people over the next 30 years - or grow by the size of Tauranga every five years.