Posted on July 2, 2025
A once-struggling stormwater pond in the heart of Warkworth has undergone a remarkable transformation, becoming not just a better water manager, but a small powerhouse for environmental restoration and carbon reduction.
The Alnwick Stormwater Pond, built in 2007 to protect local streams and filter water flowing into Mahurangi Harbour, had become clogged with sediment and plagued by erosion. By 2024, nearly half of it was filled with silt, and its outdated design was limiting its ability to do its job.
Enter Auckland Council’s Healthy Waters team and Glasgow Contractors, who saw more than a repair job; they saw an opportunity to bring nature and sustainability together.
Healthy Waters Sustainable Value Team Manager Leigh Steckler says restoring Alnwick Pond wasn’t just about fixing stormwater issues.
“It was about restoring natural function, improving habitats for wildlife, and doing it all with as small a carbon footprint as possible,” Ms Steckler says.
Before dredging of the silt began at the pond in August last year, more than 100 eels were carefully relocated along with several nesting birds, highlighting the project’s focus on environmental care from the get-go.
Sediment was removed using low-impact amphibious Truxor machines, which are floating workhorses that gently scoop silt without damaging banks or stirring up too much of a pond’s delicate ecosystem.
Alnwick Pond, Warkworth showing some of the silt and sediment removed.
Much of the silt that was dredged, more than 600 tonnes, was reused on-site, saving an estimated 4,500kg of CO₂ emissions. Some was even trialled as future cropland soil using a muck spreader, as part of Glasgow Contractors’ push to reduce landfill waste.
Native plants were also used to stabilise banks instead of concrete, locking in carbon and improving resilience.
“We planted into biodegradable coir logs and coconut matting,” explains Steckler.
“They hold the bank while providing a natural growing environment plus it looks a lot better than concrete!”
Coir matting on bank of Alnwick Pond, Warkworth.
Eco-friendly design choices continued throughout the project, from using low-carbon cement pipes to recycling aggregate from other sites; every step was made with sustainability in mind. Even a local farmer benefited, taking away road materials that would have gone to landfill, for use on his property.
And the pond restoration project didn’t just help the planet; it supported eight local businesses and the broader Warkworth economy by providing work for drainage contractors through to fencing and haulage services.
Healthy Waters General Manager Craig Mcilroy says this kind of work shows how infrastructure and nature can work together.
“We’re proud of the outcomes at Alnwick Pond, not just cleaner water, but lower emissions, stronger biodiversity, and a better outcome for the community.”
With another 2,650 native plants due to be planted along the pond’s edge in spring 2025, the renewal of Alnwick Pond is far from over.
But for now, it stands as a quiet, green success story, proof that even stormwater ponds can be heroes when sustainability leads the way.
