Channeline’s bespoke GRP liners were recently utilised on a section of Watercare’s $1.4 billion Central Interceptor project in Auckland.
Watercare’s $1.6 billion Central Interceptor is the largest wastewater project in New Zealand, featuring a 4.5m diameter tunnel that will run for 16.2km under Auckland city and the Manukau Harbour.
The giant tunnel will reduce wet weather overflows into streams and beaches in older suburbs where there is a combined wastewater and stormwater system, which becomes overwhelmed in heavy rain by taking flows to Māngere Wastewater Treatment Plant for processing.
Seventeen shafts are dotted along the tunnel route, connecting the local wastewater network to the tunnel. The new infrastructure will enable future urban growth and improve resiliency for the existing wastewater network. The project is being delivered safely, on time and almost to budget by Watercare and the Ghella–Abergeldie Joint Venture (JV).
Channeline’s glass reinforced plastic (GRP) liners were used to deliver one of these critical chambers at a site in Tawariki Street, Grey Lynn.
The existing Tawariki local sewer needed to be removed to allow construction of the new control chamber. At the time of the project, Tawariki was a double brick-lined ovoid sewer approximately 100 years old and in need of a face-lift.
Here, Channeline liners were used to strengthen the existing sewer upstream and downstream of the chamber. A flexible joint was installed at the interface of the chamber and existing sewer to allow for differential settlement.
“With a 100-year-old, double brick-lined, ovoid sewer, you can’t just go cutting through the middle of it and expect nothing to fall away,” JV Project Engineer Ollie Sefuvia told Trenchless Australasia.
“That’s why we used Channeline’s GRP liner to stabilise the existing sewer. Part of that liner is also cast into the chamber walls.
“Currently, the GRP runs all the way through our chamber to maintain flow. When the project is commissioned, that small section of the GRP will be cut out, allowing the flow to drop down into the chamber as intended.”
The Channeline factor
One of Channeline’s core strengths lies in its bespoke design and manufacturing approach. Whether it’s lining a severely deformed box culvert, a large-diameter brick sewer, or a non-standard egg-shaped stormwater pipe, Channeline’s liners are custom-engineered to suit the exact geometry of the host structure.
The Tawariki local sewer project was no exception. Channeline manufactured several 1.5m diameter ovoid liners in multiple lengths (2m, 1m and 0.9m) to create the perfect length for the existing structure. Custom lifting hooks were added onto the liners, with the longer 2m lengths having as many as six hooks, which were used to suspend the liners within the structure.
Sefuvia said Channeline’s GRP liners were selected for the project due to their simplicity, unique shape, affordability, and lifespan.
“Channeline is good to deal with. We had a single point of contact, the design drawings arrived fast, and they got the liners to us quickly,” he said.
In the end, the new chamber in Grey Lynn was executed without issues, with Sefuvia and the team soon to put the finishing touches on it.
Thanks to the combined efforts of Watercare, Ghella–Abergeldie JV and Channeline, the Central Interceptor project continues to advance, with an expected end date of mid-2026.
For more information, visit channeline.com