North Shore City Council is restricting new connections to its wastewater system in a prime redevelopment area because an ageing main sewer cannot cope.
Councillors were told yesterday that overflows from the 45-year-old Birkdale sewer were an unacceptable public health risk.
The sewer serves 10,000 people and overflows30 times a year in wet weather.
But recent growth in housing and plans for intensive development at Highbury Centre meant daily overflows in dry weather were likely in the next year or two, said wastewater planning engineer Phil Jaggard.
Constant sewage flow would cause excessive bacteria levels in the Eskdale Stream which flows into the Upper Waitemata Harbour.
Mr Jaggard said upgrading work was scheduled to take place during 2008-2012 as part of the council's Project Care - a $300 million plan to control pollution over 20 years.
But there was a case for more urgent action.
Further investigation showed the sewer was performing worse than expected and in recent months the council had learned of a number of plans to build apartments and offices in the catchment.
The council had approved 78 development sites of varying size that were not yet connected to the wastewater network.
On top of that, applications for resource consent had come in for 250 new dwellings for 700 people.
Infrastructure and environment chairman Tony Barker said the biggest one was Westland Development's plan for four-storey apartments in the much-needed redevelopment of the Highbury Mall.
"This is a prime area for multi-unit development," Mr Barker said.
He said the pipeline had given concern since the late 1990s.
The solution was now estimated to cost $15 million compared with an earlier estimate of $11 million.
Others serving Northcote Pt and Birkenhead Pt also needed upgrading.
He said a report was needed on the legal risk of the council refusing new connections to the wastewater network.
Officers were assessing applications on a case-by-case basis.
Some developments could wait two years for connections until the sewer network was upgraded in their areas.
The council voted to bring forward the project to begin next year and to allocate extra money so it could be completed in four years instead of six.
