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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.”

Chemical storage: Dominion Salt chooses APD

Mount Maunganui chemical manufacturer Dominion Salt has selected Auckland’s APD for the design, delivery and installation of multiple new storage tanks which improve the company’s production processes. By choosing APD, Dominion Salt has received cost-effective, reliable plant with proven longevity.

Dominion Salt harvests salt from the waters of the Southern Pacific, then refines and delivers the product to a range of diverse industries and destinations around the world. Founded by George Skellerup in 1942 and operating initially from Lake Grassmere in the South Island, the company opened its Mount Maunganui plant by 1974. The Bay of Plenty refinery receives raw salt from Australia, processing it into finished food, pharmaceutical, industrial and agricultural grade salt shipped to customers internationally.


Dominion Salt Site Engineering Manager Tim Knowles explains that on arrival, raw salt is mixed with water to form a brine which undergoes a purifying process. “We required two new vessels for this process, one with a 30-kilolitre capacity and another of 16-kilolitres, for pharmaceutical and food grade salt, respectively.”

The selection of APD for the job, says Knowles, was somewhat straightforward. “There are basically two options for this application: steel or High-Density Polyethylene. We already have several HDPE tanks on site supplied by APD which have been performing well since 2009, so the choice was obvious.”


Manufactured in Auckland from HDPE PE100, both tanks are open topped (exposed to the atmosphere). This required care in shipping, as the weight of the vessels could cause their collapse.

Unique designs for the vessels include, in the case of the 30-kilolitre tank, an offset agitator which required welding a bush to the base which now accommodates a shaft running 4.7 metres from top to bottom. Additionally, both tanks feature horizontal baffle plates which prevent settling. “The way APD welded and secured these features is brilliant. The tanks have a long-life expectancy and that includes the fixtures and fittings inside them. The manufacturing is top notch and can be expected to last,” Knowles notes.

Furthermore, it is well known that even stainless steel will corrode in the presence of sodium chloride. By contrast, chemically inert HPDE doesn’t react with any of the chemicals used in the salt production process, combining longevity with low maintenance and reliability. The APD tanks are also far lighter than a steel counterpart, easing handling and installation.


While the Coronavirus lockdown struck during the delivery of the project, Knowles says APD responded rapidly to keep matters on track. “There were impacts on costs and timings, but we can’t complain. APD kept us posted at all times, so we could adapt together to an evolving situation.”

The new tanks are deployed towards the end of a production process designed to eliminate impurities by holding the liquid and allowing completion of a chemical reaction. “The tank is a delayed reaction vessel which allows all solids to dissolve and remain suspended in the brine, after which the solids are removed,” says Knowles.

Rather than increasing production per se, he says the new tanks increase the volume available to complete the purification process. “Before the introduction of these tanks, we were encountering issues with sediment build-up in the filtration systems owing to limited volumes. Now we have an improvement in efficiency as there is more room for the chemical reactions to fully take place before the next phase in our process.”

In conclusion, Knowles says APD is a trusted partner relied upon for the delivery of lightweight, cost-effective and chemically resistant tank solutions. “The tanks are built solid and fit for purpose. And, in fact, they work so well on site that we already have another order in for more.”

Parker Hannifin Chem Waste/Rinse Tanks


This project was a combination of open top rectangular Process Tanks, Chemical Waste and Rinse Tanks to fit under a series of open top rectangular Process Tanks.

Custom Specification

The Tanks were designed in accordance with the BS EN12573 standard for rectangular tanks and were built in polyproylene. A pressurised PVC Filter Housing was also designed and built to capture contaminates from the process.

So in total, two Process Tanks, and two Waste and Rinse Tanks were built as part of the project, with the largest tank being a tee shaped tank, with an overall length of 6.1 metres and 1.7 metres across the head of the tee.

All of these tanks were exported to Australia to be used in part of the upgraded Parker Hannifin manufacturing plant in Brisbane.

Oceana Gold 10,000L Lime Slurry Tank and Mixer


This is a 10,000L HazSure® Tank designed for a lime slurry mix and was designed with a side manway, with 17 nozzles fitted to it, plus 3 internal baffles to improve mixing of the lime slurry.


The Tank is designed in accordance with BS EN 12573 and APD’s approved COP. APD also designed and supplied the Mixer Bridge, Ladder and Handrail for the tank.

The Ladder and Handrail were designed in accordance with AS1642 and are made from steel and coated in a generally chemical resistant polyurethane powdercoat. The Mixer was designed and supplied by Mixtec Engineering for the application.

Jasol NZ Manufacturing Plant


In 2012 APD Ltd was awarded the contract for the supply and installation of Chemical Storage Tanks for Jasol NZ’s new manufacturing plant in Auckland. In total, 14 tanks, made up of 4 indoor mixing process tanks and 10 outdoor storage tanks were fabricated and installed.

In addition to the Hazardous substance tanks, APD designed the piping layout and supplied and installed approx 2kms of piping, including manual & pneumatically operated valving and batch controllers. The pipework was a mixture of PE100, Schedule 80 PVC and Schedule 80 CPVC.

As part of this new plant, there were a number of steel structures, that included process tank platforms, one of which was five meters wide by twenty meters long, finished with GRP grating. APD was responsible for the design and installation of these platforms.

Within the manufacturing area and below the raised platforms, APD fabricated and installed HDPE bund liners. These bunded areas were setup with raised GRP grating to allow for easy cleaning and a safe none slip work area.

HazSure 20,000L Self Bunded Tanks


APD recently designed and fabricated two HazSure 20,000L self-Bunded tanks for Balance Agri Nutrients. Both chemical tanks were specifically designed to meet the requirements to store Hydro-Fluoro Silicic Acid with a design life of 25 years. These tanks were fabricated from HDPE. APD uses PE100 black pigmented sheet which is specifically designed for long term UV exposure and chemical resistance.


The tanks were designed and fabricated in accordance to BS EN12573, EN1778 and our COP 4-3. On completion the tanks and bunds were hydrostatically tested for leaks before final assembly.

APD selfbunded tanks consist of a unique compact double wall design which prevents rainwater from entering the bund.

Galvanising Process Tank Liner

A Recent project was the fabrication of 3 very large Tank Liners for a Taranaki based Galvanising company. The liners were made from black PE100 sheet and were made with the ends of the tanks thicker than the rest of the liner body to provide increased resistance to damage due to the nature of the items being processed.

The liner dimensions were 8.8m Long, 1.65m Wide and 2.81m High and are designed to store Hydrochloric Acid.

The Liner was fitted with support strips welded to the base to hold items off the bottom of the tank while being processed. The project also required special consideration on how the liners would be lifted and placed into the concrete tanks and were therefore fitted with lifting lugs to ensure ease of handling and minimize and Health & Safety concerns. Due to the nature of the liners, spark testing of the joins was used to ensure the liner integrity.

The liners were manufactured in-house at APD’s Auckland Factory and shipped to site.

Ecolab HazSure® Process Mix Tanks


This project was carried out for Ecolab New Zealand for their Te Rapa Plant. The purpose of this project was to upgrade their plant equipment allowing them to manufacture a new product in house.

The scope of the project required Ecolab to have two HDPE HazSure® Plain Tanks with Conical Bases and Mixing Baffles, allowing them to manufacture their finished product solutions in the tanks and then completely empty the tanks after manufacturing. The tanks are mounted on stands to allow for piping to connect to the lowest outlet nozzle.


APD was also contracted to carry out the design for the pipework layout for these tanks.

The pipework layout incorporated equipment such as Pumps, Static and Eductor type Mixers and Surge Dischargers in the line to allow for an adequate chemical mixing. The pipework and equipment was mounted on a stand to keep it off the floor.

60,000L HazSure® Tank


In October of 2014, APD designed and built what is to date the largest Polyethylene Bulk Hazardous Storage tank in New Zealand. The tank is a multilayer design in accordance with BS EN12573 and EN1778 with additional FEA analysis work performed to meet the client’s specification which is as follows;

With a working volume of 60,000L, this tank can accommodate a long term internal pressure of 1.5Kpa and a maximum internal pressure of 2.7KPa and its designed for seismic loading.

It has a 600mm side entry manway and a top mount inspection hatch for ease of access and various fittings to suit level measurement, of inlets and outlets.

It has a ladder with cage and a handrail to ensure safe access for maintenance and inspection purposes of the equipment. It also has tank vent and overflow connected to passive scrubbers to capture the Hydrochloric fumes during filling and emptying of the tank.


30 Sec HazSure® Process Tanks & Pipes


As part of an upgrade to the 30 Seconds Ltd manufacturing facility, APD was involved from an early stage with 30 Seconds in this important capacity & HSNO upgrade of the plant.

After extensive consideration and planning a design layout was settled on. This involved APD designing, fabricating and installing 7 x 7,500L HazSure Polyethylene Self Bunded Tanks. Each HazSure® Tank was fitted with a range of fittings to suit the unique requirements of the manufacturing set up and this included a special sloping floor in a number of the tanks to maximize emptying of the tanks between batches.

In addition to the tanks, APD also supplied and installed the chemical inlet, re circulation and outlet pipework, bracketing and labeling to 30 seconds and HSNO requirements including pressure testing on completion. UPVC schedule 80 pipe was used for all of the chemical pipework.

Here is what 30 Seconds had to say about APD’s work on the project;

“I wish to express our thanks to Advanced Plastics & Design for the recent completion of plant refit.

All aspects of the job have been completed to a very high standard with the result been we now have a very functional plant that is operating efficiently and compliant to HSNO regulations.

Throughout the design and installation, your team have been able to offer different ideas with practical solutions to some of the special requests we required on this build.

The install team were very accurate with all aspects of the installation with regards the tank placement and pipe layout. They advised us of any small detail that may have needed alteration, and they showed a high level of workplace Health & Safety as they worked. They worked efficiently, tidily, and were very courteous to our staff.

30 Seconds Ltd is proud of the final work and have no hesitation in using APD in the near future, as we undertake Stage 2 of the project with addition of several more chemical storage tanks”.

Brian Vercoe
Manufacturing Services Manager
30 Seconds Ltd