Christchurch City Council staff are formally backing away from a controversial proposal championed by Mayor Phil Mauger to pump millions of litres of partially treated sewage into Pegasus Bay each day. The move comes as councillors prepare to vote on urgent solutions for the city’s beleaguered wastewater treatment plant.
Instead of the ocean outfall, which drew widespread condemnation, staff have recommended a plan to increase aeration in the plant's oxidation ponds. This option is described in a new report as more cost-effective, less damaging to the marine environment, easier to implement, and importantly, it has the support of mana whenua.
The recommendation marks a significant turning point in the city’s struggle to manage a persistent and foul odour that has plagued eastern suburbs for years, a problem that reached a crisis point following a fire at the Bromley wastewater treatment plant in 2021.
A putrid plague on the city
The persistent stench has become a torturous daily reality for residents in the city’s east since a major fire destroyed crucial components of the Bromley facility. The situation intensified over the recent summer, with the regional council, Environment Canterbury (ECan), receiving more than 7600 odour complaints from residents in the eastern suburbs and even the central city.
The city council attributed the worsening smell to heavy rain, which reduced oxygen levels in the treatment ponds, along with seasonal algae growth. The escalating public outcry led to ECan issuing a formal abatement notice in late February, compelling the council to produce a comprehensive plan to fix the issue or face potential prosecution.
Days after the notice was served, Mayor Mauger publicly floated his proposal to divert between 45 and 55 million litres of partially treated wastewater per day straight into Pegasus Bay via the existing ocean outfall pipe. The idea was immediately met with alarm, with ECan's director of operations, Brett Aldridge, stating at the time they were "surprised and concerned" by the comments.
A 'Victorian' solution
The mayor’s plan faced sharp criticism from environmental experts, including ecologist Dr Mike Joy, who labelled the practice of discharging sewage into oceans and rivers as "Victorian." He warned that the term "treated wastewater" can be misleading, covering everything from simply removing solids to full purification.
We should be way past this kind of attitude that it's all right just to dump the waste. this old saying when there were a hell of a lot less people on the planet that the solution to pollution is dilution, but it's not that at all - the solution to pollution is assimilation." {"type":"in_body_image","url":"https://ffqbmbvywrypmfjybtyu.supabase.co/storage/v1/object/public/article-images/council-staff-reject-mayors-ocean-sewage-proposal-2.webp","alt":"Christchurch City Hall exterior with staff members debating a sewage proposal near the entrance.","caption":"City Hall staff reject the mayor's controversial plan for ocean sewage discharge into Pegasus Bay."}
Dr Joy explained that even if chlorine is used to kill bacteria harmful to humans, it does not make the discharge safe for the environment. He said the influx of nutrients from sewage drives algal blooms, which can lead to deoxygenated "dead zones" where marine life cannot survive. He dismissed the council's alternative proposal as another "ambulance at the bottom of the cliff," advocating instead for a long-term solution like an industrial wetland system.
New rules and rising risks
The debate is intensified by new national wastewater standards that came into effect in December. Council's wastewater treatment plant operations manager, Adam Twose, told a community board meeting in March that the ocean diversion plan was only being considered because the new regulations were "significantly more relaxed" than the plant's current resource consent conditions. "Under the new wastewater standards, there's the option to go a lot looser, so you're allowed to discharge more contaminants to the environment," he said.
Dr Joy argues this represents a "completely backward step" for environmental protection in New Zealand. "The only performance that will improve might be the economic bottom line for these councils because they'll be able to get away with dumping more of the stuff without treating it," he says.
However, the water services regulator, Taumata Arowai, defended the new rules. Spokesperson Sara McFall noted that with over 20 per cent of the country’s wastewater plants on expired consents and half of the underground pipe networks in poor condition, the regulations were designed to make urgently needed upgrades affordable.
Council staff have now presented six options to councillors, but recommended only two as viable. The primary option involves increasing aeration in the ponds, at a cost of $7.7 million to $11.2 million. A second, more expensive option, costing up to $16.6 million, would add aeration and allow for some diversion of partially treated wastewater to the ocean for a limited number of days per year. Staff noted this discharge would still contain contaminants and there had been no time to assess the full ecological or public health impacts.
Council under pressure
The council is facing pressure from multiple fronts. On Tuesday, ECan's Brett Aldridge confirmed the regional council was now reviewing the city council's new proposed plans. This came just after ECan issued a second abatement notice in March over a series of illegal sewage discharges into Whakaraupō Lyttelton and Akaroa harbours, prompting local hapū Ngāti Wheke to consider legal action.
City councillor Yani Johanson says it was always obvious the mayor's ocean pipe plan was unrealistic due to the significant risks and environmental concerns. He expressed frustration that the more practical solution of increasing aeration had not been proposed sooner.
"Many of us around the council table have asked for options to address what was going on and what was causing it for years. I welcome the idea that we can do more, but it's frustrating it's taken this long to get to that point," Johanson says. He is now calling for better council oversight of the long-term project to build a new activated sludge plant, which isn’t due for completion until 2028. This long timeline is one reason that short-term solutions are desperately needed for a city that is also looking forward to major projects like the new Te Kaha stadium.
Johanson is also pushing for council staff to prepare a plan to directly support the affected community, suggesting measures like free GP visits for residents suffering health effects, the creation of a register for vulnerable people, and the distribution of air purifiers. "While there's some things being done," he says, "there's no clear plan that the community can look at to hold us accountable for mitigating the impact on their health and well-being."
