Whanganui District Council has begun a staged programme to remove sand and sediment from the Castlecliff water network, following successful trials of specialist filtration equipment, including a trial within the live network yesterday.
The trial demonstrated sand could be removed from the network using the specialist filtration system while maintaining safe water supply to connected properties.
Whanganui Mayor, Andrew Tripe says the council is prioritising the safety of the water supply as it works to resolve the issue, with the successful trial being a significant step forward and providing confidence to begin work across the wider network.
“This week’s successful trial is a significant step forward in addressing the sand issue. It gives us confidence to begin working through the wider network, while continuing to take a careful and methodical approach to avoid disturbing sand and sediment in other areas,” said the Mayor.
The affected network has been divided into six areas, with work planned to progress one area at a time following yesterday’s trial. Results will be assessed before moving to the next area, allowing the council to adjust the approach if required.
The NO-DES mains cleaning creates a temporary loop through hydrants, circulating water through filters before returning it to the network. This is the first time it has been used in Whanganui, although it has been used by other water providers in New Zealand and Australia to remove sediment from drinking water networks. It also reduces the amount of water released onto streets and into stormwater.
“We’ll monitor the effectiveness of NO-DES as work progresses through the network and keep the community informed. We’re also providing schools, industry and plumbers with practical information about what to expect, what they need to know and how we can help. Our focus is on making careful progress, getting this right and supporting the community throughout,” said Mayor Tripe.
He acknowledged the ongoing disruption for the community from the unprecedented event.
“We recognise how frustrating and disruptive this has been for affected households. This week’s result is encouraging, but we know there is still work ahead of us. Our focus is on progressing that work as quickly and safely as possible while continuing to support the community. We appreciate how understanding and patient the community has been.”
The issue emerged after water-main upgrade work in early September, when higher water flows appear to have disturbed sand and sediment in a reinstated part of the network at Westmere reservoir. The issue has been intermittent, with some households experiencing sand, sediment or discoloured water.
The Council continues to use specialist advice to guide the staged work, monitoring and next steps.
“Disruption to households and businesses has been at the forefront of our minds when planning this work, however we cannot guarantee that people won’t notice changes to their drinking water while the work is underway. We encourage the community to contact the council if they do notice any changes such as sand, sediment, or discolouration,” says Mayor Tripe.
