Christchurch Wastewater Treatment Plant update

Tuesday 10 March

Pond condition stable 

Conditions across the ponds have remained stable since last week, with no changes to the odour status tracker. Overall pond health remains fragile – pond 2B is showing some positive response, while ponds 1 and 2A are holding steady but still not in strong condition.

We’re continuing hydrogen peroxide dosing, and the percarbonate trial at the temporary activated sludge plant is ongoing. We used the jetboat late last week and it remains on standby.

With a mixed weather pattern ahead – cooler nights, warmer daytime temperatures, shifting winds, and periods of calm – intermittent odour is possible at times. While we don't expect these conditions to create strong, sustained odour, they can allow odour to linger or move into different areas depending on wind direction and strength, especially as the ponds continue their gradual transition toward winter-mode conditions.

We’ll continue daily management actions and close monitoring to respond quickly to any changes.

Ocean outfall 

Our team continues to investigate the possibility of diverting some treated wastewater to the ocean outfall. There are important steps we need to work through before this plan can progress.

New hydrogen sulphide monitoring dashboard launched

Our new hydrogen sulphide monitoring dashboard shows the hourly averages of hydrogen sulphide measured at each of our five monitors. Just select a location on the map to see the latest H₂S level for that monitor. 

Please note:

This dashboard provides monitoring information to support community awareness. While Christchurch City Council always works to make sure the information is accurate and up to date, data may occasionally be delayed, incomplete, or unavailable due to operational or technical factors. 

Comparing hydrogen sulphide levels by location 

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

The long-term fix: Activated sludge reactor construction update

Construction of the new activated sludge reactor is progressing well, and it remains the key long-term solution to odour from the wastewater treatment plant following the fire.

Excavation at the new plant site is now well advanced, and we’ve started sheet piling along the temporary pipeline, as seen in the picture above with the orange digger driving into the ground. As part of this stage, we’ll monitor vibrations throughout the construction and implement mitigation measures where possible to minimise the impact on neighbours. 

The installation of stone columns is also ramping up, with subcontractor setup underway and trials planned for this month. If the trials are successful, we'll start installing those columns in earnest after the Easter break. 

Design work is progressing in parallel, including the development of the new odour treatment system that will operate alongside the reactor once it is complete.

The first set of pipes have been packed up and are on their way to New Zealand.

We’ll continue to share updates as the project moves through its next construction phases, and you can view monthly progress videos on the project webpage.

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.