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The Challenge

Faced with a growing population and the effects of climate change, Auckland’s regional water supply is under increasing pressure. So in 2020, as part of an ongoing programme to expand Auckland’s drinking water supply, Auckland Council’s Watercare Services greenlighted a shovel-ready project to refurbish Hays Creek Dam, a decommissioned 1950’s treatment plant, fed by an 18.2 hectare lake holding 1.1 gigalitres of water.

Work began on the project in October 2020 and just four months later, in February the Hays Creek Dam was brought back into service with a temporary water treatment plant, adding an additional six million litres a day to Auckland’s water supply. The completion of the permanent plant in late 2021 will see peak production doubled to supply 12 million litres a day.

Our Task

APD was engaged by Suez Australia to supply the chemical treatment and holding tanks for the temporary Hays Creek treatment plant, with work on the permanent plant to follow. When lake water leaves the dam, it passes through a series of filters and treatment stages to eliminate any contaminants and biologicals. APD was tasked with designing 45,000, 37,000 and 11,000 litre holding tanks for the chemical treatment processes as well as a 60,000 litre tank to hold wastewater that was not cleared for release into the water supply. These would be some of the largest tanks APD has made to date and they would need to be designed and manufactured to extremely high tolerances and very tight deadlines.

“Every country has different requirements for water processing.” says Frank Vergan, Senior Site Leadership Manager with Suez Australia. “In New Zealand, those standards are particularly high. Working with a top local manufacturer like APD ensures that the tanks and structures are all fit for purpose and meet local standards and regulations. As we had worked with APD on smaller projects in the past, we were confident that they would deliver to the standards required for this project.”

The APD Solution

Designed using SolidWorks and manufactured in APD’s Auckland factory, the HazSure holding tanks for the Hays Creek temporary plant are constructed from heat welded, High Density Polyethylene (HDPE). To withstand the pressure of huge amounts of water, HazSure tanks are designed with a tapered profile that is thicker at the base and with horizontal baffle plates in the base for seismic stability.

HPDE does not react with chemicals and its low maintenance and durability made it the ideal material for building the HazSure® storage tanks. Because HPDE is much lighter than steel, it also made the logistics of transporting such large tanks a lot easier, particularly as they had to be trucked up a steep hill into the Hunua Ranges. The tanks have a minimum life expectancy of 25 years and can be completely recycled once the temporary plant has been decommissioned or possibly recertified and utilised elsewhere.


Working through the Coronavirus lockdown, APD designed and delivered the HazSure tanks for the Hays Creek temporary treatment plant, on time and to budget. “I’ve worked with suppliers all around the world.” says Suez’ Frank Vergan, “But I can’t speak more highly of the quality of the manufacturing and service APD brought to this project.”

“On a fast tracked project like this, there’s always a lot of pressure and the COVID restrictions had a major impact on our supply chain. We had to rely on local suppliers a lot more than we might normally for a project of this size, but the workmanship and the quality of the support we received from local companies like APD was outstanding. It certainly provided valuable learnings for us going into the next phase of the development.”

“We’ve enjoyed an awesome relationship with Suez on this project.” says APD Design and Projects Engineer Jamsheed Tata. “Having Frank here in New Zealand has been a huge benefit as we could collaborate and solve issues very quickly. We’re committed to building long term relationships with our suppliers and customers and we see our relationship with Suez continuing to grow as we work together on the permanent treatment plant.”


  • HazSure Custom designed, HDPE chemical storage tanks.
  • 60,000L, 45,000L, 30,000L and 11,000L capacity.
  • Minimum 25-year design life, fully recyclable and reusable.
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