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.
High river flows result in the water becoming more turbid (dirty) forcing the plant to require more backwashes.
What is a backwash?
It’s a method used to clean filter media (usually sand or another granular substance) 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.
What is damaged?
We have had independant engineers do a structural assessment on the options on how we can get the plant back to normal operation.
Both the backwash filter and pipework is damaged, beyond repair. Both the filter and pipework are over 40 years old and age is likely to have been a factor.
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.
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 option that also has a similar lead time (approved by the scheme committee).
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.
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.
Updates
We will keep you updated as the work progresses. These updates will be put out via the following Council channels.
- 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
