Fixing Auckland's stormwater and wastewater systems will cost hundreds of millions of dollars, but some lobby groups are worried that will still not be enough.
Areas in West Auckland have been flooded by water systems unable to cope with heavy rain. Photo: RNZ / Cole Eastham-Farrelly
The Auckland council has set a $450 million water rate to fund required work on the city's water infrastructure.
That includes seeking a 35-year consent to discharge stormwater through the city's public network and over land.
The council received about 80 submissions in response to the consent application, which closed in March.
Interested parties would be consulted ahead of a hearing on the application which had been confirmed to take place in September.
Some lobby groups who submitted opposing the consent were concerned it would not be enough to solve problems, such as stormwater overflowing the sewerage system in heavy downfalls.
Liz Walker from the St Luke's Environmental Protection Society told Nine to Noon that in her area in Auckland's west, manhole covers blew out in heavy rain, throwing up all sorts of things which people have put down their toilets.
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She said that happened largely because the area had combined sewers handling wastewater and stormwater.
"So small sewers which could handle sewage in dry conditions are now required to handle all the rain, and rain is very variable. Often it doesn't take very much rain at all for these manhole blowouts to happen in parks, which is clearly a big health risk.
"What happens with the rest of it is that the stormwater, the sewage and 50 percent of the combined sewers have run off from our roads, so [there are also] the heavy metals."
Ms Walker said the material also flowed down to the harbour, which caused more problems.
"The sewage then does not flow out on the next tide, it in fact sloshes around in the harbour for two or three days after a decent rain event and comes in and out, in and out.
"[It then goes] along what were wonderful beaches.... reaching the point where they're closed because people feel unsafe, which is a total shock to people like me."
Photo: RNZ / Nikki Mandow
Manukau Harbour Restoration Society spokesperson Grant Hewison said the main problem was there had not been investment in Auckland's wastewater and stormwater systems for decades.
His group would like an assurance that a half-billion dollar wastewater project - the central interceptor - is not the council's only solution for the stormwater problems.
He said 20,000 10-tonne truckloads of treated wastewater were being discharged into Manukau Harbour each day.
"The central interceptor is just a massive holding tank, so when it rains at one end of the western isthmus the combined waste water and stormwater will go into that pipe. It will basically fill up and then be treated over time through the Mangere treatment plant.
"But that's going to increase that 20,000 10-tonne truckloads maybe by twice that amount and we're going to continue putting that water into Manukau Harbour."
Mr Hewison said the group was also concerned that when it rained the treatment plant was bypassed, allowing only partially-treated or screened wastewater to go directly into Manukau Harbour.
Manukau Harbour Photo: RNZ / Jessie Chiang
He said dealing with wastewater was a core function of council business that was as important as transport and there was a pressing need for areas with old infrastructure - such as Herne Bay and Grey Lynn - to have new systems implemented separating the stormwater and wastewater.
Council water manager Andrew Chin said there were questions around how to manage contaminants and water quality, while also trying to manage the effects of flooding.
He said separating the wastewater and stormwater was also part of the plan.
"We have to do both; increase the size and capacity of the wastewater system to cope with growth and minimise flows, but we'll also be separating."
Mr Chin said fresh approaches were also being tried in new developments, including a shift to what he termed a 'water sensitive' design approach.
"If you go and look around quite a lot of the new greenfields developments, you'll see quite a different urban landscape.
"You'll see rain gardens in a lot of places, nearly every house in a new development will have a water tank to mitigate the run-off of water in that hard surface and these rules are coming in slowly. A lot are included in the unitary plan."
Some lobby groups have questioned whether Auckland Transport should be contributing to the water projects, but Mr Chin says it already did.
"Their assets are the catch-pit. All of the catch-pit cleaning - the sumps catch a lot of nasty heavy metals and sediment and they fund all of the maintenance on those."
Mr Chin said fixing Auckland's water problems was a gradual process as there were not endless coffers available to rebuild the city just for the sake of improving water quality.
"Aucklanders have spoken and they're prepared to pay for a targeted water quality rate which is certainly a first in my career as a water engineer, having dedicated funds towards water quality improvement.
"But it is just a start and the important thing is we build a process by making sure we leverage those redevelopment opportunities."
Meanwhile, Ms Walker said money must be spent separating out the water system.
She said central government also had a role to play and an independent regulator could be the only way to get any reconciliation between the 3-year political terms and the 100-year investment life-cycles for these kinds of assets.
Auckland mayor Phil Goff had previously urged support for a tax to help clean up the city's beaches.