No more red ponds!

Here's some good news as we head into the long weekend - the last of the oxidation ponds - pond 1 - has improved enough to be able to turn it orange on our pond tracker! This means the health of all the ponds has reached a point where the levels of hydrogen sulphide and odours being emitted from them are low.

While pond 1 has reached the threshold to be turned orange, it's almost certain that it will remain at this level for the foreseeable future.

This is because pond 1 has a larger sludge blanket at the bottom than the other ponds. While this isn't abnormal for an oxidation pond system, we would like to see the sludge levels decrease. However, this is a slow, natural process that could take months before our survey work records any noticeable reduction. 

So why do we turn ponds 'orange' or 'green', even when the two-week average is below the benchmark? You can read an explanation of this by clicking the green button below.

Don't clean paint-staining off your house this long weekend 

This long weekend, it might be tempting to clean any discolouration off your house that might have been caused by a chemical reaction between lead paint and hydrogen sulphide. 

We ask that you to please keep waiting. We're hearing anecdotally that paint-staining on houses is starting to naturally decrease now that the hydrogen sulphide levels have reduced and daylight hours are lengthening.

Before we begin encouraging people to clean their homes, we'd like to see at least a couple more weeks of low hydrogen sulphide levels and improved weather. This will give us an idea of how discolouration fades in direct sunlight. 

If you absolutely must clean your house now, make sure you're familiar with our list of dos and don'ts (link below).

We strongly recommend you don't use a high-pressure washer, as this could lead to flakes of lead-based paint entering the environment.

If your home has paint-staining and you haven't let us know, please get in touch by emailing wastewater@ccc.govt.nz. We'll add you to a special database and provide you with advice and updates.

 Hydrogen sulphide levels remain very low

Every Wednesday we upload the past week's data for the continuous air monitors that have been set up near the Christchurch Wastewater Treatment plant.

The monitors are to detect the levels of hydrogen sulphide in the Shortland Street and Rudds Road areas, as well as at Bromley and South Brighton Schools.

We're now seeing a significant and sustained drop in hydrogen sulphide levels across all sites, helped by both the improving oxidation pond health, and the stronger spring breezes that have helped dissipate any odours more quickly.

Note the readings online are only up until Friday 14 October – we'll publish graphs showing this week's  levels of hydrogen sulphide next week once the data from all of the sites has been collated.

You can read the data for all locations, and an explanation about how to read the information by clicking the link below. You can also find past readings for each site.

Stay updated

We want everyone to be able to stay updated on our response and recovery from the treatment plant fire, and we regularly post new information and reports on ccc.govt.nz/wastewaterfire 

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 in advance for your patience and understanding as we continue to work on minimising the unpleasant smells after the fire. We’ll be in touch again soon.