Stirling Water Treatment Plant
October 2024 flooding event
The water supply to Stirling and Benhar, Cherry Lane residents comes from the South Bruce Rural Water Scheme. On Wednesday 4-5 October 2024 Clutha experienced extreme rainfall that targeted certain areas of the district more than others.
In July, mid-winter, river flows are typically 300-550 cubic metres per second (cumecs). At its peak during the flooding event it reached 1940 cumecs, which the plant simply could not cope with that amount of water.
The plant’s damage from the flooding was extensive making water treatment impossible. Consequently those residents living in Stirling, Benhar, Cherry Lane and the South Bruce Rural Water Scheme were put on a boil water notice.
During flooding events high river flows result in the water becoming more turbid (dirty) forcing the plant to require more backwashes.
Unfortunately it will take some time to source and undertake the work to repair the plant and we expect the boil water notice to be in place until 2025.
What is damaged?
Both the sand filter and backwash pipework is damaged, beyond repair. Both the filter and pipework are over 40 years old and age is likely to have been a factor.
We have had independent engineers do a structural assessment on the options on how we can get the plant back to normal operation.
Repair update 23/01/2025
Progress is continuing on the repair of the Stirling Water Treatment Plant however there will be short delay to the previously reported timeline.
The repair design was finalised in December and essential equipment was ordered. A local contractor removed the damaged floor and the damaged pipework in the sand filter.
The first stage of the concrete floor pour was deferred and not poured until the new year. This did not cause any delay to subsequent stages being undertaken.
The new floor and nozzles, along with reinforcing steel were installed and the coating of the tank structure was completed on Tuesday.
The floor holding the 660 new nozzles will need an additional concrete pour, which had not been identified in the original plan. The second concrete pour is planned for tomorrow (weather permitting).
Once cured the next steps will be to reload filter media and recommission the plant. The repairs are expected to be fully completed by mid-February.
Following this we will begin reticulation sampling and flushing of the network.
The Council thanks you for your patience and understanding while the works are being completed.
Restrictor cleaning
Customers on the South Bruce Rural Water Scheme may notice a lower flow of water going into their tanks, since the flooding event held in October 2024.
If you are experiencing low flow into your tank please check your wire strainer at your tank's restrictor and do a simple clean. This might resolve the lack of water going into your tank.
You can read the step-by-step cleaning guide here:
Repair options
Several replacement options were considered. One included a temporary containerised filter system however, there were long lead times for these options to be sourced.
It was decided to select a permanent refurbishment of the existing filter that also has a similar lead time (approved by the scheme committee).
What is a backwash?
It’s a method used to clean filter media (usually sand or another granular substance such as activated carbon) by reversing the flow of water to wash out accumulated debris and particles. The process effectively removes unwanted contaminants, rejuvenating the filter media and thereby extending its life cycle.
Why a boil water notice?
Sand filter is a critical stage of the treatment process. With this unavailable it removes a barrier to treatment and can make disinfection stages less effective.
We cannot guarantee that water will consistently meet the requirements of the New Zealand Drinking Water Quality Assurance Rules and our regulator requires suppliers to take action and a Boil Water Notice is typically the standard response.
Temporary water Supply
You can fill your clean containers at the water tank available at the Stirling Athenaeum Hall and a water tank has been set up at Cherry Lane for residents living at Cherry Lane to use.
Future updates
Future updates will also be put out via the following Council channels. Sign up and stay up-to-date.
- Antenno app (download the from the App Store or Google Play)
- Text and email alerts (subscribe online: www.cluthadc.govt.nz/subscribe-forupdates
- Water alerts are also posted on Council’s website www.cluthadc.govt.nz/water-alerts
We understand that some of our community might struggle with technology and we ask family and friends to help spread the word.
You can read our boil water FAQs at: www.cluthadc.govt.nz/boil-water-faqs
