Christchurch Wastewater Treatment Plant update

4 September 2024

The science behind winter odour 

During winter, odour from the Wastewater Treatment Plant and oxidation ponds can get trapped closer to the ground – due to Christchurch's inversion layer – and take longer to disperse. Here's a summary of how it works:  

When it's still and cold an inversion layer develops in the air over our city. This is caused when the ground cools off rapidly making the air closest to the ground much cooler than the atmosphere layers above. Moisture also comes from Pegasus Bay and this produces a dense, low-hanging cloud that blankets the town, and particularly the eastern suburbs.

The Port Hills to the south of the city act as a barrier, preventing air from circulating and moving away, especially when there is a light north or northeast wind.

Cold moist air and warm dry air do not mix very easily, so the warm dry air acts like a blanket trapping cool moist air below. This means that odours released from the plant as well as smoke from fires and emissions from car exhausts are trapped close to the ground and take longer to disperse. 

Recap on the insurance process 

Christchurch City Council completed the concept design for restoring the trickling filters in May. Further investigations and more detailed design work are underway. The design is to restore the trickling filters to their pre-fire state, but with some changes to allow for current best practices, modern equipment, and safety standards.  

In the meantime, Christchurch City Council continues to work productively with its insurers to resolve the insurance claim for the Christchurch Wastewater Treatment Plant. While this process is ongoing, we're not able to release more detailed information without prejudicing the insurance claim or disclosing confidential commercial arrangements. We’re committed to making more information available to the public once the claim is resolved.

Monthly community board updates 

Every month our staff give the Waitai Coastal-Burwood-Linwood Community Board an update on the Wastewater Treatment Plant.

You can attend in person to hear the updates. Livestreams and recorded meetings are also available on YouTube. 

Hydrogen sulphide monitor results 

Monitoring results have shown that levels over the past month have been decreasing and are now very low. At times light winds may still carry hydrogen sulphide, and other odours, to nearby residential areas but the levels are now very low. 

Health and wellbeing 

Health New Zealand has informed us that there are various services across Ōtautahi Christchurch available to support and enhance overall health and wellbeing. Below you will find a list of services and contacts. These services include Health Improvement Practitioners (HIPs), Support Workers and Pae Ora ki Waitaha who offer free support for mental and physical health.

Health Improvement Practitioners (HIPs)

• HIPs are qualified and experienced mental health professionals who work in General Practices (GPs).
• They work with individuals of all ages, including whānau.
• Sessions are brief (15 to 30 minutes), focusing on strategies and goals that will help you to make positive changes.
• There are no restrictions on the number of sessions you can have. 
• This service is free.

Contact your local GP to book in and enquire, or find out more here. 

Support worker

• Support workers operate within the community to assist you with factors affecting your wellbeing. They may visit you at home or connect you with broader community services, including cultural support, physical activities, housing, and social services.
• This service is free.

Contact your local GP to book in and enquire, or find out more here. 

Pae Ora ki Waitaha Support

• Pae Ora ki Waitaha is a healthy lifestyles service developed with Māori and Pasifika providers.
• The service is free and supports individuals to improve overall health and wellbeing.

Find out more here. 

Stay updated

We want everyone to be able to stay updated on our response and recovery from the treatment plant fire, and we regularly post new information and reports 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.