Christchurch Wastewater Treatment Plant update

Wednesday 11 February 

Thank you 

We want to start with a thank you to all the residents we spoke with during yesterday’s neighbourhood visits. The kindness, openness, and understanding we received at your doors meant a great deal to our team. We know the stench has been challenging, and we truly appreciate the time people took to talk with us.

Our team visited 750 homes and received 545 responses. For those who weren’t home, we left a calling card with our contact details. If you’d like to speak with us, please give us a ring and leave your name and phone number – we’ll happily arrange a time to call you back.

A clear message came through in our conversations: you want this issue resolved as quickly as possible, and we hear you. These visits were an important step in listening directly to the community, and we’re committed to doing more of this – spending real time with people, answering questions, and hearing concerns firsthand.

We’re now reviewing all the feedback gathered yesterday and developing a set of potential community support options. These will be presented to the elected Council for consideration and approval.

More updates to come as this work progresses – thank you again for your time, your honesty, and your continued patience.

Improving access to hydrogen sulphide information

We know the community is eager to have clearer, more up‑to‑date information about hydrogen sulphide (H₂S) levels, and we want to reassure you that this work is a priority for us. Our team is committed to improving transparency and making it easier for residents to understand what’s happening in their area.

We already have strategically placed hydrogen sulphide monitors around the oxidation ponds and nearby neighbourhoods to track levels, and we’ve doubled our odour assessment frequency, with updates now posted twice a week on our website.

Behind the scenes, we’re working on the next stage – making indicative additional hydrogen sulphide data available directly on our website. Once the dashboard is ready, residents will be able to view more recent readings at a glance.

There’s still some technical and testing work to get through before we can launch this, and while we don’t yet have a confirmed launch date, we want you to know that this is well underway. We’re pushing it forward as quickly as we can and we’ll continue to keep the community updated as the work progresses.

Activated sludge reactor update – all go on site! 

Work on site is progressing well, and excavation is now in full swing. Crews are steadily removing soil from the site, with the average depth reaching about two metres below ground. This will create the platform needed for installing the stone columns later on.

Next week, the team will move closer to the plant to carry out some exploratory work. This includes locating any existing services that may still be in the ground from the old trickling filter and removing what’s no longer needed. Doing this will allow us to install sheet piling and safely excavate along the temporary bypass line that was put in after the fire.

For the next few weeks, the focus will be much the same – dig, dig, and more digging – as we continue preparing the site for the next stages of construction.

The overall programme is expected to span about three years, with commissioning targeted for 2028. Importantly, we’re able to build the new activated sludge reactor with minimal disruption to current operations.

A full project timeline outlining each stage of the work is available on our website if you’d like to see how the schedule unfolds.

Pond condition stable 

Conditions at the ponds remain much the same today. Algae numbers are slowly increasing, which is an encouraging sign and an important part of the recovery process. However, there is still odour coming from the ponds, and Pond 1 continues to struggle.

Alongside our immediate work to support recovery, we’re also looking ahead to what can be done in the long term to reduce the chance of another odour event in the future. This work needs to be robust and sustainable, and while it will take a little time to finalise, it remains a high priority and is being fast-tracked wherever possible.

Our teams are working incredibly hard – both to get the ponds healthy now and to take on board the lessons that will help us improve moving forward.

Actions underway 

• A batch of sodium percarbonate has been delivered to site for trial use. Staff are preparing systems to enable dosing to the temporary activated sludge plant as required to improve oxygen levels and support plant performance.
• We've been dosing the ponds with hydrogen peroxide and additional product has been ordered and will be delivered to site.
• Three new aerators installed on Ponds 2A and 2B are fully operational. Staff are closely monitoring performance, particularly in relation to potential odour generation from the new aerator installed on Pond 2B earlier this week.
• A specialist wastewater pond expert has been engaged and will be on site this Thursday and Friday to support the development of a comprehensive pond management plan.
• The jet boat has again been deployed today to provide additional oxygenation to the ponds.

There is no change to the odour status map today. We’ll continue to provide updates as the situation evolves.

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.