• Innovative Swiss technology in use in New Zealand for the first time to remove and sort sediment from stormwater ponds
• Around 14,000 cubic metres of sediment, equivalent to five and a half Olympic swimming pools, removed from our stormwater ponds last year to protect Auckland’s streams, estuaries and harbours from sediment pollution.
• Up to 60 per cent less sediment from ponds will be sent to landfill due to the new tech.
First-of-its-kind Swiss dewatering plant trial in Wairau Valley showcases a smarter, lower-carbon approach to reducing sediment waste.
Innovative Swiss technology is being used in New Zealand for the first time to tackle one of Auckland’s largest waste challenges while helping protect the region’s streams, estuaries and harbours.
A Swiss-engineered mobile dewatering plant, being trialled at a stormwater pond in Wairau Valley on Auckland’s North Shore, is set to transform how sediment is removed from the city’s 650 stormwater ponds before it enters our waterways.
Stormwater ponds are critical to managing the city's water quality. They capture and treat run-off from roads, rooftops and car parks before it reaches our waterways — trapping sediment and contaminants that would otherwise smother aquatic life.
Without them, significantly more pollution would flow directly into Auckland's harbours.
Around 14,000 cubic metres of sediment is removed from stormwater ponds annually, to ensure they continue to operate effectively. Over the next 20 years, approximately 2.2 million cubic metres of sediment will need to be removed from Auckland’s stormwater ponds and disposed of. Until now, that sediment has been sent to landfill.
North Shore Councillor Richard Hills says the technology being trialled has the potential to reduce sediment going to landfill from stormwater ponds by 60 per cent. It will also reduce the carbon emissions and disturbance from the trucks that transport the sediment for disposal.
“The health of our waterways is a priority for Aucklanders, and these ponds play a vital role in stopping sediment reaching our streams, estuaries and harbours,” says Hills.
“If we can transform how we remove the sediment from these ponds, we will significantly reduce the waste going to landfill and the carbon emissions associated with transporting that waste.”
Unlike conventional methods, the mobile plant processes sediment on site, stripping out water and separating sand, gravel and stone in a single operation. The separated fine gravel and sand may potentially be reused as fill or aggregate to make site concrete. The remaining silt may be used on site for topsoil and planting. The result is a much smaller and lighter waste stream, meaning substantially fewer truck movements, lower disposal costs and a significantly reduced environmental footprint.
Healthy Waters and Flood Resilience Head of Sustainable Partnerships Tom Mansell says the timing is critical, with many of Auckland’s ponds now requiring major sediment removal for the ponds to operate at full capacity.
“Last year the equivalent to five and a half Olympic swimming pools were removed from our stormwater ponds,” says Mansell.
“This technology has the potential to reduce the volume of material sent to landfill by up to 60 per cent by separating and recovering sand, gravel and water on site rather than disposing of the whole lot."
Kade Glasgow, of Glasgow Contractors who imported the Swiss technology, says the Wairau Valley project provides an opportunity to assess the system’s wider potential.
"This new system is capable of extracting a much higher percentage of dry solids from the sediment than the 10 to 20 per cent from using conventional methods — that's what we're here to test and verify,” says Glasgow.
“If the trial proves successful, it could deliver meaningful reductions in landfill volumes, truck movements and carbon emissions across Auckland.”
This week, the Swiss Ambassador to New Zealand, Viktor Vavricka, visited the Wairau Valley site to see the innovation in action.
With millions of cubic metres of sediment requiring removal in coming decades, the technology offers a smarter, lower-carbon approach to maintaining the infrastructure that protects Auckland’s waterways and harbours.