The current wastewater treatment plant at Akaroa. Photo: Supplied/Christchurch City Council
The Christchurch City Council is defending its moves to press on with long-awaited multimillion dollar sewage plant upgrades for the Banks Peninsula township of Akaroa.
The proposed $94 million dollar facility north of the town is set to service a community of less than 800 people, at a cost of more than $120,000 per resident.
It would also mean Akaroa's existing wastewater treatment plant at Takapūneke will finally be decommissioned.
Plans for the new plant, north of the town, have found support with leaders of local rūnanga Ōnuku.
But they continue to be met with resistance in other quarters, with some residents describing elements of the scheme as "abhorrent".
For more than 60 years, the town's wastewater has been treated at a facility situated in the culturally significant Takapūneke Reserve and discharged into the nearby harbour.
Takapūneke was the scene of a brutal massacre in 1830, known as the "Elizabeth Affair", when a Ngāti Toa war party raided the kāinga and slaughtered hundreds.
A rubbish dump was also established on site in the late 1970s, before it was capped in 1999.
"It is now widely acknowledged that the construction of a wastewater treatment plant at this site was an act of particular cultural insensitivity," it states on the council web site.
A wastewater-to-land-irrigation system would replace the existing facility, involving treated wastewater being reused to irrigate neighbouring farmland, as well as native trees and plants at Hammond Point and Robinson's Bay.
The council has applied for resource consents to set up and operate the scheme with hearings resuming in a fortnight.
Friends of Banks Peninsula deputy chair Suky Thompson said the flawed plan was too expensive for what it was.
"For that amount of money, we would expect to get a system that didn't experience overflows into [Akaroa Harbour] and set us up well for climate change in the future and address chronic water shortages that we're likely to face," she said.
"This proposal, even though it's so expensive, doesn't do any of that."
The problem lay with Akaroa's shaky sewage network, particularly its high infiltration / inflow (I&I) issue.
Thompson said the facility would not have the capacity to accommodate high levels of stormwater infiltration during extreme weather events, resulting in raw sewage being discharged onto the waterfront of the Akaroa Recreation Ground.
"At the moment, the plan sanctioned by Ōnuku Rūnanga is for [untreated wastewater] to be discharged right on to the foreshore, that is into a very shallow coastal estuary.
"We think that is completely abhorrent and completely unacceptable."
Despite this, the universal feeling among locals is that the plant should be relocated from the "culturally significant heritage site" of Takapūneke, Thompson said.
'Overflows are going to happen'
Council head of three waters Gavin Hutchison said under the proposed scheme, untreated discharges were estimated to happen "once every five years".
But the price in mitigating these overflows had been deemed unrealistic, with council staff wanting to "strike a balance between investment and protecting the environment".
"It will happen, it does happen on all wastewater schemes," Hutchison said.
"In a scenario where have high rainfall events and you have flooding on the roads and on private property, the amount of stormwater getting into the sewer does increase substantially."
"We could always design to address that, but the cost to address that becomes astronomical."
Similarly, Ōnuku Rūnanga chair Rik Tainui said finding a "perfect system" was unfeasible, but the new scheme would reduce instances of untreated wastewater entering Akaroa Harbour.
Between 2020 and 2024 there were 22 occasions where untreated wastewater was discharged into the harbour, including 15 from Akaroa, five from Duvauchelle, and two from Tīkao Bay.
Fourteen of these instances were due to rainfall events overwhelming the scheme.
In response to calls that Akaroa's dubious I&I symptom of its network needed to be remedied first, the council said the town was not alone.
"We've got worse instances of I&I in the city.
"Ageing infrastructure is a problem that all New Zealand councils have to contend with."
A total of $5m had been spent on wastewater repairs and renewals of the Akaroa network over the past four years.
All private properties in Akaroa and Duvauchelle had undergone checks for stormwater infiltration of drainage systems.
The council admits it is also up against the clock to finalise a new wastewater plant, with consent to discharge wastewater into Akaroa Harbour expiring in 2030.
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