A strong smell has continued to blanket parts of Christchurch, prompting Environment Canterbury to step in as thousands of complaints mounted over the city’s wastewater treatment plant.

Environment Canterbury Chair Dr Deon Swiggs said it was critical people understood the difference between the regional council’s role and Christchurch City Council’s responsibilities.

“The city council own this asset. It is their asset. They need to do the compliance and they need to make sure that as part of the condition of the consent which the regional council gives to the city council that there is no odour or smell or stink leaving the boundary of their facility,” Swiggs said.

He said Environment Canterbury became involved once the smell moved beyond the boundary of the plant.

“What we have seen over the last couple of weeks is there has been a bit of odour, well a lot of odour, leaving the boundary of the sewage treatment plant, which is where our role comes in from a compliance point of view,” he said.

Environment Canterbury received a surge of complaints as the smell worsened.

“Over the weekend we had 2,000 complaints. Since about the 26th of January when this really started to get bad, we have had nearly 4,000 complaints,” Swiggs said.

He said the council had increased its presence on the ground, with staff speaking directly to residents.

“We had 14 field staff in the field over the weekend. Fourteen of our staff were out talking to residents. It was not just about compliance for us. It was also about talking to residents in the worst affected areas so they feel like they are being listened to and that this is being taken seriously,” he said.

Swiggs said Environment Canterbury could not force the shutdown of a major piece of infrastructure.

“We cannot force the council to shut a major facility down like the sewage treatment plant. That is just unrealistic,” he said.

Instead, he said the focus was on bringing Christchurch City Council back into compliance.

“We need to work with the city council to understand how they will get back into compliance, what steps they will do, and then that needs to be communicated to the communities and to the wider city so people understand what is going on,” Swiggs said.

He said health impacts were a serious concern and had been acknowledged nationally.

“We have had health advice from the Ministry of Health and the medical officer of health has put out a statement saying the odour will cause headaches, nausea, and some residents have said they feel sick and have not gone to work. It is causing very real issues for people,” he said.

Swiggs said it was up to Christchurch City Council to explain how it would manage the problem.

“They need to come out and say this is what we are doing, this is how we are going to manage the stink, and this is the timeframe to expect us to get back into compliance fully,” he said.

He said he could not comment on possible enforcement outcomes while investigations were underway.

“I cannot go into the details of an investigation or what outcomes might be because I cannot prejudice any form of outcome that may happen,” Swiggs said.

After visiting affected suburbs, Swiggs said the experience was confronting.

“It is horrible. I live in the central city and on Thursday night last week it was so bad that even my eyes were stinging, and I am not in the worst affected area,” he said.

“You go closer to the sewage treatment plant and your eyes do water, they do sting, and you just feel unwell inside,” he said.

Swiggs said residents had every right to be frustrated.

“I do empathise and understand how people are feeling. We are sorry for how this is affecting them. It is not good enough,” he said.

“Let’s get on top of it. Let’s make sure it does not happen again and let’s get a clear path moving forward about what the long term solution looks like.”