Council’s revised plan to fight stench
Christchurch City Council has come up with a revised plan to reduce the latest stench coming from its wastewater treatment plant, following an official censure.
But people are being warned the stink could increase for a couple of weeks as winter arrives.
The regional council, Environment Canterbury (ECan) says the city council’s plan is sufficient to address and continually monitor the odour in the community and on site.
ECan issued the city council with a significant non-compliance notice on February 19 after it received 162 odour complaints in the three months to January.
The odour was substantiated by ECan three times. The plant’s consent, issued by ECan in 2016, stipulates no offensive or objectionable odour beyond the plant boundary.
The smell started coming from the plant after two trickling filters were destroyed by fire in November 2021, taking out 60% of its treatment capacity.
Staff were able to keep the plant operating, but the stench from the damage tormented residents, causing nausea, headaches, respiratory illness, sleepless nights and mental health impacts.
Temporary measures helped some, but residents are still reporting the smell.
ECan requested the council provide it with answers on what was causing the most recent odour and provide indepth detail on specific actions to mitigate the stink.
The council had until February 29 to do that, but requested an additional eight days to submit the information, which was granted by ECan.
ECan zone manager Johannes Welsch said the organisation would continue to proactively monitor odour in the area and ensure compliance with the conditions of the consent.
When asked what action would be taken if there were future breaches, Welsch said the response would depend on the circumstances and the nature of the incident. “This is very much a case-by-case basis.” City council head of three waters Brent Smith said the plan outlined many actions the council was taking to address the issues, improve the performance of the plant and lessen the impact on the community.
“We’ve had a hot and dry summer which means the sewage entering the plant is more concentrated and anaerobic. When you combine this with hotter temperatures you end up with an increase in odour.”
He said an intensive monitoring programme had helped the council identify a range of sources at the plant, and work was underway or planned to address these.
Some of the actions in the plan include ensuring the pond aerators are more reliable and available to work at maximum capacity. Staff were also now removing smelly scum build up in the primary settlement tanks each day.
One of the main sources of the odour over the summer was the primary settlement tanks.
“We’ve decreased the amount of time sewage is held in the tanks and early indications show this has reduced odour.”
Smith warned that the biology of the ponds would change as winter arrived, which was likely to result in a couple of weeks of increased odour.
“We can’t predict exactly when this will happen, but we’ve got a plan ready to go to minimise odour through this period.”
Smith said the recent increase in smell was a significant cause of stress for the community the council was committed to doing everything it could to minimise the smell.
Cr Yani Johanson said there was technical work being done to determine the cause of the odours, and a comprehensive report was due in early April. “The insurance needs to be sorted and we need to give the community confidence that the permanent fix is happening as a top priority”.
He said more support was needed for residents’ health and wellbeing, especially with the work ongoing.