Christchurch Wastewater Treatment Plant update

Wednesday 4 March

We know many of you will have questions following the Mayor’s announcement on Monday that we're looking into sending partially treated wastewater directly to the ocean outfall pipe.

This is one option we are actively investigating, and it is still in the early planning stages. Staff are looking at whether we could divert a proportion of treated wastewater flow so it goes straight to the outfall pipe instead of through the ponds. Reducing the load on the ponds would help lift oxygen levels and ease the conditions that create stench.

There are important steps we need to work through before this plan can progress. We'll continue to update you through this newsletter and on our website. We’ve added a new drop‑down section to the common questions page so you can easily find the latest information related to this option.

Spikes in odour possible

Our latest pond monitoring shows a small improvement in the health of ponds 3 and 4, which have moved from red to orange on our odour status tracker. This is a positive step, and we’ll keep watching these ponds closely over the coming days.

However, the current cold snap could potentially result in an increase in odour. Cold temperatures slow down algae growth, which reduces the natural oxygen in the ponds. The forecast shows warmer and more settled weather. These conditions can cause hydrogen sulphide to linger above the ponds and move into nearby suburbs, so we expect some ups and downs in odour levels.

Our teams are continuing daily actions to support pond recovery, including:

• ongoing hydrogen peroxide dosing to lift oxygen levels
• sodium percarbonate dosing
• close monitoring of water quality and algae health

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.