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Hurunui Mayor Marie Black with the excited kids from Leithfield School

Hanmer Springs completes major redevelopment

Constructing New Zealand’s largest waterslide and the country’s most sustainable thermal pools was always going to be a challenging project. Doing it in an iconic tourism hotspot that values sustainability just added even more complexity.

The renowned Hanmer Springs Thermal Pools and Spa in North Canterbury attracts more than half a million people every year: it’s one of New Zealand’s busiest tourism attractions. And 8 November 2019 was a big day for the complex’s management and staff and the construction project team when Hurunui Mayor Marie Black and a classroom of excited kids from Leithfield School were given the honour of officially opening New Zealand’s largest waterslide, Conical Thrill, and five new thermal pools, The Cascades.

The $4.5 million developments were constructed over eight months. It wasn’t a straightforward job, requiring innovation, collaboration and enormous attention to detail. But thankfully, the team behind the new developments had the skills to deliver these incredible additions that will be cherished for generations to come. And like any other project, it began with a clear vision.

Designed with care

For those readers who haven’t been there, Hanmer Springs is a picturesque village surrounded by mountains and forests 90 minutes north of Christchurch. It’s quaint, with a population of less than 1000 residents who are understandably passionate about their place in the world.

Hanmer Springs Thermal Pools and Spa’s general manager Graeme Abbot says that passion, and the fact the complex is owned by the Hurunui District Council, means the community takes special interest in the complex.

At the official opening ceremony on 8 November 2019 – the facility incorporates materials from Canterbury, giving the pools an authentic sense of place – Photos courtesy of Claudia Lewis Photography

“The new developments had to be designed with care and sustainability in mind. We went to enormous effort in the planning phases to ensure that both additions would be beautifully landscaped with native gardens, and that Conical Thrill, in particular, wouldn’t impact neighbouring properties.

“We also had to take time to consult with our community to ensure they were across the detail of the design and that the resource consent process would run smoothly. We’re delighted to say we didn’t have a single submission against the consent application, so construction was able to get underway ahead of schedule.”

Innovation-driven sustainability

Rough and Milne Landscape Architects was tasked with designing the new developments. Director Tony Milne says Graeme’s team came with a very clear vision, particularly for The Cascades.

“They wanted the pools to look as natural as possible and for bathers to be able to soak amid the sounds of rushing water in a tranquil setting. They also needed the pools to accommodate up to 180 people at a time, so we knew they had to be at least 180 sq m in size.”

The Rough and Milne design team set to work on a number of options, taking cues from Canterbury’s natural landscape. The end design was a series of five rounded terraced pools that are linked by waterfalls and cascading waters.

Tony says the design utilised materials from Canterbury, giving the pools an authentic sense of place. “The Cascades are surrounded by more than 100 greywacke boulders that were carefully selected and locally sourced. We’ve also used large engineered slabs of Timaru bluestone and plants that are native to the area.”

One of the key engineering challenges was ensuring the waterfalls and cascading rapids would not cool the pools down. Tony says expertise within the pools’ management team helped overcome this. “The complex’s engineering and operations manager, Neil Wilson, was the brains behind that and many of the pools’ sustainability features. With Neil’s help, we were able to alter the design so that the waterfalls and rapids are in fact a separate system of cooler water that doesn’t enter the bathing areas. It’s quite genius.”

Neil also ensured the design delivered New Zealand’s most sustainable thermal pools. “The pools are super water efficient and have no balance tanks. We’re also capturing waste heat from a methane generator and some good old Kiwi ingenuity to help power them,” says Neil.

That generator is a story in itself. In 2018, the pools installed New Zealand’s only micro turbine methane-powered generator to use waste methane from the site to generate electricity. The award-winning project now produces 14% of the complex’s electricity and stops 101,000 cu m of the greenhouse gas from being released into the air.

Once the generator was up and running, management noted the enormous amount of heat that came off it. Under Neil’s guidance, they decided to capture that and, through a heat transfer unit, it now provides half of the energy needed to run the new pools and slide.

Graeme Abbot says the innovation is another first for New Zealand and it’s all down to Neil’s ingenuity. A typically humble Neil simply says, “It was great to see it all come together.”

Construction challenges

Another key challenge was ensuring that the construction of the pools did not damage the roots of the 90-year-old giant redwood trees nearby. Lead contractor O’Brien Construction director Peter O’Brien says the solution was to build them, unlike most other thermal pools, above ground.

“We installed 184 timber piles and the pools are suspended on these. This minimised ground disturbance and is possibly a first – I haven’t heard of another pool being built on timber piles.”

Once out of the ground, Peter says they faced more challenges. “The curved design was tricky to construct for our block layers, and the use of so many natural materials meant we had to work closely with both Rough and Milne and the project engineers during construction.”

Installation of the 13.5 m Conical Thrill was challenging – the slide arrived onsite in more than 150 pieces, and supporting infrastructure includes four big columns and extensive foundations

That collaboration was particularly important when it came to the installation of the 100 boulders. Ben Bellamy, from Rough and Milne, handpicked the exact boulders he wanted for the project and was onsite when they were installed to guide the O’Brien team on where each should go to achieve the design.

“Tony and Ben’s guidance was important,” says Peter. “We also had the engineers alongside us and did a lot of preplanning around the boulders’ install. These are natural rocks that are not designed to fit together, so in some cases we had to design and build as we went. Simply put, Ben would guide us as to where each boulder needed to be, and we would work with the engineers to build a structure to support it.”

Considering that each of these 100 boulders weighed up to 600 kg and they had to be craned into place, you can further understand the complexity of the build. Despite these challenges, construction was finished to schedule and to budget.

Precision engineering for Conical Thrill

Cequent project manager Nick Radburnd says the installation of the 13.5 m Conical Thrill, which arrived onsite in more than 150 pieces, was equally challenging. “The slide was designed out of Canada and the fibreglass sections manufactured and shipped to site from the Philippines. While the team from WhiteWater West was putting the slide together, O’Brien Construction was tasked with building the infrastructure that would support it.”

Peter O’Brien says the job required precision. “Conical Thrill sits on four big columns, the tallest of which is 12 m high. The foundations underneath are extensive. The key thing was ensuring that when each of the columns was craned into place, it was perfectly positioned. We couldn’t risk the slide, which twists and turns, not fitting, so we used a surveyor to ensure accuracy down to the millimetre. It was very technical work.”

Students from Leithfield School testing Conical Thrill – the class won a competition to become the slide’s first official riders

The construction team also had to extend the complex’s existing hydroslide tower by 3 m. “That meant we had to close the tower’s top levels at different times and work with the pools’ management team to ensure it was open for peak times, including the July school holidays. It was all about collaboration.”

Graeme Abbot says thankfully the expertise of all involved meant the job was completed without a hitch. “The excitement certainly grew as the slide came together, and it created enormous interest among our visitors. Once it was completed, we then had to do the fun part – extensively testing it.”

A successful end

Anyone who saw the Leithfield School class – that won a competition to become the slide’s first official riders on opening day – will know from the excited faces that the testing was successful. For Graeme Abbot, that day signalled a successful end to three years of hard work.

“It was magic and the weeks since have been equally so. Our visitors are absolutely loving the rush of Conical Thrill, but also the tranquillity of soaking in our famous mineral-filled waters amid the sound of rushing waters in The Cascades. We are very proud of both these additions. I regularly look at them and think, ‘Wow – how lucky are we?’ We know they will delight visitors for many years to come.”


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