Christchurch Wastewater Treatment Plant update

Tuesday 24 March

Algae levels improving

We’re seeing another week of encouraging progress across the oxidation ponds. Algae activity is flourishing, and as a result we’re seeing high numbers of daphnia (water fleas).

The bright red areas visible in photos taken yesterday (shown below) are daphnia. Their high numbers show the ponds currently have plenty of food (algae) available and that these organisms are thriving in the conditions.

Pond 2b

Pond 3

Pond 4

Odour status tracker 

Because of this sustained improvement in the ponds, we’ve updated the pond odour tracker – none of the ponds are currently sitting at red.

While this is a positive milestone, there is still a risk of odour as we move through seasonal changes. Transitions in weather and temperature can cause shifts in oxygen levels and pond biology, which may lead to short‑term odour spikes, particularly overnight or during calm conditions.

The long-term fix: stone column pile installation underway

Work on the activated sludge reactor progressed into its next major phase on Monday, with the installation of stone column trial piles now underway. The trial will finish by the end of this week, and the stone column installation will begin soon after the Easter break. Some nearby residents may notice vibrations from the equipment during this stage.

A reminder that:

• From Easter, this phase of work will take approximately four months to complete. Following on from the stone column installation is the pipe installation work, which will require the installation of more sheet piling and is likely to take about one month. We'll let you know about timeframes closer to the time.

• Work hours are Monday to Saturday, 7.30am–6pm

We know the vibrations can be unpleasant, and we’re monitoring the work closely to minimise impacts where possible.

To date the levels recorded on the site boundary are well below the level set for damage to buildings but we are aware the vibrations are within nuisance levels. Our focus is on completing this phase safely and efficiently so we can move on to the next stages of construction.

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.