Devonport sewer upgrade reducing overflows
North Shore City ' s five-year, $14 million investment in repairing or replacing Devonport ' s leaky sewers looks set
to pay off with tests showing the extensive work is halving the amount of rainwater leaking into the pipes and far fewer
sewage overflows expected as a result.
The Devonport project has been undertaken as part of Project CARE, North Shore City ' s $210 million, 20-year programme
of work to improve beach water quality. Back in 1998, the council set a target of reducing wet weather sewage overflows
events from approximately 12 to an average of two a year.
North Shore City Council ' s works and environment committee chairperson, Joel Cayford, says that to date all the
public sewers identified as needing repair have been completed.
" Results show that the amount of stormwater leaking into the Devonport wastewater 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 721 out of a total of 1439, are still to be
upgraded by property owners, " Councillor Cayford says.
" The Devonport project was our city ' s priority because leakage of stormwater into the pipes in Devonport overloaded
the wastewater network (to the Rosedale wastewater treatment plant), all the way to Wairau and contributed to overflows
on Takapuna and Milford beaches.
" Keeping rainwater out of Devonport ' s sewers is a work-in-progress which will probably never finish. But once the
remaining private sewer lines are brought up to standard and through regular inspections to identify new leaks, we will
have a drainage system that is the best we can reasonably achieve using available technologies, " says Joel Cayford.
The council ' s general manager of water services, Geoff Mason, says once the remaining private drains were repaired,
further reductions in the amount of stormwater infiltrating sewers could be expected.
Mr Mason says the work began with detecting leaks using smoke, dye or closed circuit television. Leakage into, or out
of, the pipes was 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 Torpedo
Bay, and increased capacity in the network provided by the Birkley Tunnel in Bayswater, are all contributing to the
achievement of our Project CARE objectives.
" The improvements are also projected to provide sufficient capacity for Devonport ' s population through to at least
the year 2050, " says Geoff Mason.
The total cost of the Devonport sewer repair and renewal programme was approximately $14 million. The sewer repair work
is ongoing and the council ' s attention is currently focused on detecting leaks in Hauraki, Belmont and older parts of
Northcote.
Repair and renewal work in Hauraki and Belmont is expected to be finished by June next year. Detecting leaks in parts
of Takapuna and Milford will start later this year. Work will also start in older Northcote next year.