Christchurch Wastewater Treatment Plant update

Friday 30 January 

Our staff are onsite monitoring the situation in real time, taking action to stabilise the ponds, and working to minimise odour where possible. Odour is likely to continue for now, but we are doing everything we can to manage and reduce its impact.

We know the odour is frustrating and unpleasant, especially for residents living close to the plant. We want to reassure you that our staff are working hard to manage the situation.

A recap on what's causing the odour 

The recent heavy rainfall has disrupted the biological processes within the oxidation ponds. Monitoring shows dissolved oxygen levels have dropped across the system. Low‑oxygen conditions make odour more likely, especially in Ponds 1, 2 and 3, which are currently the most affected.

In past wet‑weather events, additional rainfall has supported pond recovery. This time, the ponds have not responded in the usual way. Increased inflow and load into the system have added further pressure, increasing the likelihood of odour.

We know the smell is unpleasant and disruptive, and we are sorry for the impact this is having on you and your whānau.

What we’re doing

We’re monitoring pond health and odour continuously across the plant and in the surrounding community. Staff are reviewing results and making adjustments where possible. Recent and ongoing actions include:

• Actively monitoring the temporary activated sludge system, which is performing as well as it can under current conditions.
• Adjusting flows through the oxidation ponds to reduce load and odour pressure on the most affected areas, including redirecting more flow from Pond 1 into Pond 4 to take pressure off Ponds 2A and 2B. We’re monitoring this diversion closely while gradually lowering pond water levels to improve flushing and refresh the system.
• Deploying a jet boat on Ponds 2A and 2B to introduce additional oxygen without disturbing settled sludge.
• We recently installed two new aerators on Pond 2, which are performing well, and we’re installing another aerator in mid-February to further support pond health.
• We also continue a range of monitoring including pond sludge surveys, external odour specialist reviews, checking dissolved oxygen levels, upcoming weather conditions and a range of other influencing factors.

We are carefully managing all adjustments to avoid unintended impacts from changing too many factors at once.

What to expect over the weekend 

Dissolved oxygen levels across the ponds remain low as of this morning. This means odour is likely to continue in the short term. Conditions may fluctuate depending on weather, temperature and system recovery. We will continue to monitor the situation closely and take further actions as needed.

Latest hydrogen sulphide monitoring 

The biological health of the ponds is fragile. Significant spikes of odour are being detected at community monitoring sites. Our teams are doing everything they can to address the current situation.

Health, wellbeing and support services 

There are free services across Ōtautahi Christchurch available to support and enhance overall health and wellbeing. These include:

Health Improvement Practitioners (HIPs)

HIPs are qualified mental health professionals based in General Practices (GPs). They offer free, 15–30 minute sessions focused on practical strategies to support mental and physical wellbeing. There is no limit to the number of sessions you can access.

You can book directly through your GP.

Pae Ora ki Waitaha Support

Pae Ora ki Waitaha is a free healthy lifestyles service developed with Māori and Pasifika providers.

More information is avalable on their website. 

Healthline

Healthline is a free over-the-phone health service available 24 hours a day, seven days a week. If you or someone in your family is unwell, you can call Healthline and speak to experienced nurses and paramedics for health advice and information about what to do next.  

Call 0800 611 116.

Stay updated

We want everyone to be able to stay updated on what's happening at the Christchurch Wastewater Treatment Plant, and we regularly post new information on ccc.govt.nz/wastewaterfire 

You're welcome to send this update to your networks. If you know someone in the community who doesn’t have email or internet access, please print this newsletter off and pass it to them.

If you know of anyone who would like to receive this e-newsletter they can subscribe online. 

If you have any questions, or would like further information on the project, please call us on 03 941 8999 or 0800 800 169 or email wastewater@ccc.govt.nz  

Thanks for your patience and understanding. We’ll be in touch again soon.