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Customer: Watercare Services Ltd Contract type: Design and Construct Location: Glen Eden, Auckland, New Zealand   |
Fast Facts
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We upgraded Glen Eden's wastewater infrastructure, using innovative construction methods to reduce our footprint and lessen the impact on residents. The network upgrades have reduced the number of overflows that occur following prolonged heavy rains.
The design and construction of a 2 million-litre storage tank under an existing car park in Harold Moody Reserve using a caisson method was a creative solution to space constraints..We also used trenchless tunnelling methods to install the new pipelines, minimising disruption to residents living on Glendale Road.
Reducing the impact of the project for residents, drivers, and the general public was a key driver. Adopting the alternative ‘caisson’ approach significantly reduced the working space required and managed risk and cost for our customer.
The ‘caisson’ solution is rarely used in New Zealand but is more common in large European cities where space is limited.
The construction method involved the installation of a steel cutting ring at the base of the walls, followed by the subsequent casting of three 4 m high, 400mm thick concrete lifts, one on top of the other. forming a ring of walls 18.5 m in diameter,
After each wall section was cast, the earth within the ring was excavated, and with the aid of the cutting shoe, the caisson walls sank under their own weight. The annulus between the outside of the walls and the cut profile was filled with bentonite, which kept the caisson’s rate of descent even.
Another challenge was protecting and maintaining the integrity of the 910 mm diameter North Harbour Water Main, the main water source for the area, which runs directly alongside the new tank and remained live throughout construction.
The project was a collaboration between all parties, which contributed to its success by encouraging innovative design and construction solutions. The work needed to be completed in a residential area alongside a local road and between the road and recreation and sports grounds. By using the caisson method we were able to build the new storage tank in a small parking space nearby, reducing the area that needed to be closed to the public ithe storage tank Detailed planning of the access shaft locations, construction and the pipe installation method meant we could keep the site footprint to a minimal, reducing disruption to the residents, businesses and clubs.
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Other elements of the project included:
- a new tank overflow to the adjacent Waikumete Stream
- a new network sewer in Harold Moody Reserve
- 800 m of a new transmission sewer, 10 m deep, along Glendale Road from Ceramco Park to Harold Moody Reserve
- a new transmission sewer through Sherrybrooke Esplanade and Parrs Park, including a new box culvert, associated connections, and chambers
- a new network sewer from Rangeview Road to Sherrybrooke Esplanade, including drilling underneath the NIMT railway and construction of a pipe bridge over Waikumete Stream.
Watch a timelapse of the tank construction
