Christchurch Wastewater Treatment Plant update

Friday 12 December 

Thanks to everyone who joined us at the community meeting last night. We had staff and contractors on-hand to provide updates and answer questions about everything happening at the plant. If you weren't able to make it to the meeting, you can watch a recording of the presentation here, or read the rundown below: 

Activated Sludge Plant construction 

HEB Construction has been confirmed as the contractor for the construction of the Activated Sludge Plant. They will begin setting up the site on 6 January 2026, with the goal of having the construction village ready by 21 January. Ground improvement work is scheduled to start from 26 January.

We answered questions from the community about noise, vibrations, dust, and truck movements. Here’s what you need to know:

• Noise and vibration will be monitored at the site boundary, with strict limits in place. If these limits are exceeded, mitigation measures will be put in place. 
• Dust control will include visual monitoring, water carts, speed limits, and other suppression techniques to keep dust to a minimum.
• Traffic management is being planned with HEB’s ground improvement subcontractor to reduce impacts on the community. During ground improvement work, there may be up to 30 trucks per day coming to the site. We haven't yet confirmed the route trucks will take to site, but will share this once we know.  

Work hours will be Monday to Saturday, 7.30am–6pm. If any work needs to happen outside these hours, we'll notify the community in advance.

We'll keep providing updates through the usual channels – our website, this e-newsletter and on social media.

Clarifier repairs planned for next year

Repairs to Clarifier 4 are scheduled for March next year, and important preparation works are already underway. Clarifiers play a critical role in the wastewater treatment process, ensuring solids are separated from the wastewater before it enters the oxidation pond system.

What’s happening

• The Clarifier 4 drive needs replacing, and dewatering will be required to complete this work.
• A cut-off wall will be constructed first, starting in January, following a successful trial to confirm the best design.
• Once the clarifier is dewatered, there is potential for odour to increase because the treatment plant will be operating with only one clarifier during this time.

Timeline

• Cut-off wall construction: January
• Dewatering: April
• Mechanical works: June–July (approximately eight weeks)

We’ll keep the community updated as work progresses and share any odour management measures in place.

Ongoing operations 

As the weather changes, we continue to work hard to limit odour and keep the treatment process running smoothly. Here's a run-down of some of what our team's been up to: 

Odour monitoring and mitigation 

• We monitor odour at five community sites. All data is available on our website where results are published fortnightly. 
• We've purchased three new aerators for the oxidation ponds. They reduce odour by increasing oxidation and flow in the ponds. Two will be installed this month and one in January. 
• We carry out regular water sampling, take aerial imagery and keep track of bird numbers to monitor pond health.
• We also do sludge surveys which help us understand how the ponds are behaving and how we can tweak our treatment process to manage odour and midges. 
• To assist with algae growth, we have an algae pump which transfers algae between ponds.
   

Our pump in action transferring algae between ponds.

Pond odour chemical trial 

• We have been trailing a number of suppliers' products to assess if they can reduce odour from the ponds.
• The trial is complete and we're waiting on final results.
• The products have been assessed for their ability to reduce odour and impacts on pond health and pond treatment capacity. 
   

Product trial underway.

Midge management 

• We monitor midge numbers from the ponds, using both floating traps and land-based traps. We're also trialling using artificial intelligence to count the number of midges caught in our midge monitoring traps. ​​​​​
• We have trialed midge dredging on Ponds 2A and 2B while undertaking additional monitoring to assess the impact on odour. 
   

Dredging the ponds disturbs the midge lifecycle. 

Latest hydrogen sulphide monitoring 

The biological health of the ponds is fragile. Intermittent levels of odour are being detected at community monitoring sites.

Available support 

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.

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.

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.

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.