Hynds Pipe Systems has proven its ability as a leading supplier for water infrastructure through its work on a major New Zealand project.
Watercare is building a 14.7km underground wastewater tunnel called the Central Interceptor from Māngere Wastewater Treatment Plant to Grey Lynn, central Auckland.
The 4.5m diameter main tunnel is being dug by a large Tunnel Boring Machine (TBM) called Hiwa-i-te-Rangi. Two smaller link sewers will intersect the main tunnel.
Ghella Abergeldie JV is delivering the project. Construction is taking place at 16 sites across Auckland and involves the excavation of 17 shafts and associated infrastructure.
Around 500 staff are working on the $1.2 billion project, which is due for completion in 2026. It is one of the largest wastewater infrastructure project in New Zealand history and will leave a legacy of cleaner waterways by reducing around 80 per cent of wet-weather overflows in central Auckland.
This will be achieved by capturing combined stormwater and wastewater flows and sending them to Māngere Wastewater Treatment Plant for processing.
A total of 17 shafts will be constructed along the tunnel route, with the Mount Albert shaft utilising precast concrete caisson segments supplied by Hynds Precast, a division of Hynds Pipe Systems.
The Mount Albert volcanic cone site has a 39m deep by 8m diameter shaft, with the first 27m constructed using precast concrete segments.
Hynds Precast secured the license to manufacture precast concrete caisson segments ranging from 6m to 18m in diameter in New Zealand, partnering with Macrete.
Macrete, established in 1979, specialises in the precast concrete engineering industry, operating extensively in the United Kingdom and Ireland.
The company offers concrete civil solutions, covering sea defence, civil engineering, railway infrastructure, water, wastewater, and utility sectors.
Initially, concrete segments were imported from Ireland, allowing production to commence in New Zealand as soon as moulds were available, while adhering to the tight schedule.
Caisson segmental shaft construction stands out for its cost-effectiveness, efficiency, and safety when creating below-ground chambers of up to 27m in diameter.
This method is particularly suited for situations where the native ground lacks stability.
It involves the fitting of a steel cutting edge at the base of the first concrete segment ring, and the shaft is then pushed downward from the surface using hydraulic jacks, as the native ground is being excavated.
The shaft construction progresses ring by ring until the desired depth is reached.
At this site, six hydraulic jacks (with a total force of 150 tonnes) were used by the construction team to reach the solid rock formation known as the East Coast Bays Formation.
This construction technique eliminated the need for expensive internal shuttering or pile driving. Once all rings were in place, a safe working environment was established for construction crews to build the shaft base.
Hynds Pipe Systems is the flagship company within the privately owned Hynds Group of Companies, founded in 1973 by John and Léonie Hynds.
This year marks the company’s 50th anniversary. The Hynds Group supplies products for stormwater, wastewater, roading, and water management to the New Zealand civil and rural infrastructure markets. The group consists of nine business units involved in metal, concrete, plastic manufacturing, product importation, distribution, and trade supply.
This article featured in the October edition of Trenchless Australasia.
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