Our five-year, $14 m investment in repairing and replacing Devonport’s leaky sewers looks set to pay off. Tests show that the extensive work done is halving the amount of rainwater leaking into the pipes and far fewer sewage overflows expected as a result.

The Devonport project is part of Project CARE, our 20-year programme of work to improve beach water quality. In 1998, in consultation with North Shore residents, we set a target to reduce wet weather sewage overflows events from approximately 12 to an average of two a year.

All the public sewers in Devonport identified as needing repair have now been fixed. Results show that the amount of stormwater leaking into the Devonport sewer network has been reduced by 51 per cent, a significant milestone in Project CARE.

Approximately half of the private property drains needing repair, that is about 700 out of about 1400, are still to be upgraded by the property owners. Once this work is done further reductions in the amount of stormwater infiltrating sewers are expected.

Finding the problems

Work began in Devonport by measuring the sewer flows and detecting leaks using smoke, dye or closed circuit television. Leakage into, or out of, the pipes has been repaired by lining the pipes, inserting a sealant, or digging up the pipes and replacing them.

The repair and renewal programme in Devonport, together with wastewater storage facilities at Northboro and North Head, and increased capacity in the network provided by the Birkley Tunnel in Bayswater, all contribute to achieving our Project CARE target. 

The planned improvements will also provide sufficient capacity for Devonport’s population through to at least the year 2050.

Ongoing work

The sewer repair work is ongoing and we’re focusing our attention on detecting leaks in Hauraki, Belmont and older parts of Northcote.

Why Devonport first?

The Devonport project was our priority because stormwater leaking into the pipes in this poorly maintained part of town overloaded our wastewater network on its way to the Rosedale wastewater treatment plant caused overflows at beaches along the way. 

This overloading often affected our Wairau pumping station, which overflowed into the Wairau stream and onto Takapuna and Milford beaches.

Once the remaining private sewer lines are brought up to standard, regular inspections as part of our citywide programme will help to identify new leaks, so that we’ll have a drainage system that is the best we can reasonably achieve using the technologies available.

We all have to play – and pay – our part to fix the sewers to stop the flow on effect of polluted beaches.