Blowing smoke to stop Auckland's sewage overflowing
Wafts of smoke rising from houses in an Auckland suburb this week was not a sign of fire.
Instead it was Watercare blowing burnt oil fumes up Te Atatu Peninsula's wastewater pipes in an attempt to stop raw sewage flowing onto properties and into the harbour.
For years diluted wastewater has spewed out of manholes at and around Taipari Strand when there has been heavy rain, causing a health hazard and leaving behind items such as used tampons and toilet paper.
Watercare network efficiency manager Anin Nama said the same problem also happens in other parts of the city, and was caused by stormwater entering wastewater pipes.
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Finding and fixing illegal connections and leaks in the system was a solution, he said.
"Every little bit helps. Remembering that stormwater from a single house can displace the equivalent wastewater from more than 40 households, removing even a few non-compliant connections can make a real difference."
Te Atatu MP Phil Twyford said the overflows had been an issue in his electorate at least since he became its MP in 2011, but it had got worse in the past year.
"The question is why has this been allowed to go on for so long? Why are they only acting now?
"It's not acceptable in the 21st century for our city to be pumping raw sewage into the harbour and have it flooding public areas and people's backyards when there's a heavy rain storm."
But it was not just illegal connections causing the problem, he said.
"Watercare and council over a long time have got a hell of a lot to answer for because decades of neglect and under investment has meant that the infrastructure in Auckland has not kept pace with growth."
Nama said Watercare had used the smoke-blowing technique in the city previously, but were now taking a more proactive approach.
"We are doing it in more of a structured and targeted manner."
Over the past couple of months testing had been done in Mellons Bay and in Pukekohe, and other areas would follow.
The smoke was part of an inflow and infiltration inspection which also included a visual inspection of properties, he said.
These could be downpipes going into gully traps, or gully traps that were not raised above ground-level.
Of the first 150 properties tested in Te Atatu, about five were found to have bad connections. Hundreds more were yet to be tested.
"It's a low number. It's around two per cent of what we've done to date," Nama said.
Nama said property owners were given the test results, and the council attached any problems to the property file and worked with the owners to fix problems.
"Council do take a proactive approach in working with the property owner to make sure they understand the problem and are looking at options to get rid of that stormwater. They do have powers available to them and in some cases they may choose to exercise those."
Watercare was also testing and fixing its own pipes, he said.
Smoke could be seen coming from a stormwater drain that took some of the runoff from sport fields at Te Atatu Peninsula Park.
Matipo Rd resident John Seward had been affected by overflows from a manhole near his front door, which consistently flooded his driveway and garage.
He was grateful to Watercare for now installing a back-flow prevention valve to fix the situation.
But Nama said stopping all overflows in the area required several initiatives.
These included not just inspections and the smoke machine, but also diverting areas in Hobsonville and Whenuapai from the Te Atatu wastewater system, as well as optimising pump stations.