Delivering geotechnical services for the Wai Ariki Hot Springs and Spa

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Pictured at the Grand Opening: Alex Parrett, Lawrence Charles, Sam McGovern, Tetra Tech Coffey NZ General Manager Alice Chaplin, and David Sullivan

Wai Ariki Hot Springs and Spa, Rotorua celebrates Grand opening

Principal Geotechnical Engineer Lawrence Charles and Associate Geotechnical Engineer Alex Parrett provided key services to the Wai Ariki Spa Building for Pukeroa Oruawhata Group (Pukeroa) in the Rotorua CBD.

The team’s in-depth knowledge in geothermal soils as well as the settlement characteristics of the natural diatomaceous silts proved essential for this heavily and unevenly loaded lakeside structure. Tetra Tech Coffey’s involvement with the project began in 2017, taking over from the previous geotechnical engineer.

Tetra Tech Coffey provided a practical solution that included a large two-tiered preload/surcharge fill accompanied by a settlement monitoring regime where we analysed using curve-fitting techniques.  In addition, the fill raft beneath the preload/surcharge comprised lightweight pumiceous sands and gravels and was reinforced with biaxial geogrids with the lower portion below the groundwater table.

Reflecting on the project Lawrence Charles identified it was the ongoing communication between the project stakeholders throughout the entire project which ensured successful outcomes at every key milestone.

“The project involved detailed weekly coordination meetings, over an extended period, with the project manager, architect, Pukeroa, civil, geothermal well drillers, structural, and contractor to discuss progress and issues during its design and construction”, said Lawrence.

Some of the challenges faced by the team included that the project was redesigned midway through, with our specialist knowledge leading the way with the foundation and structural load changes and their effects on the now completed Wai Ariki Spa Building.

New Zealand Prime Minister Chris Hipkins attended the official opening of this world class, New Zealand-proud project on 15 June 2023, along with Minister for Regional Development Kiri Allan and Minister for Tourism Peeni Henare.

It is another great example of Tetra Tech’s Leading with Science® approach to complex, and challenging projects.

Connect with Lawrence Charles at

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