In a significant sign of progress, the first concrete pier to support the Old Māngere Bridge Replacement for walking and cycling is emerging in the Manukau Harbour.
Scaffolding was removed this week, so the “V” shaped pier is now visible above the walls of the cofferdam built to create a water-free working environment for the construction crew.
The pumps that kept the working space dry for months have been turned off, allowing the cofferdam to fill with seawater. The cofferdam will be removed in January, says Waka Kotahi Senior Manager Project Delivery Andrew Thackwray.
“This is a great achievement for the project team to end the year on. The piers are the foundations for the new bridge and once they’re all in place, work next year will be above the waterline where construction progress will be much more visible.”
The pier, constructed with 68m3 of concrete and 13 tonnes of reinforcing steel, is the first of seven smaller piers that will support the new bridge. One of the two big piers that will hold up the bridge arch is also under construction. All piers are due for completion in late 2021.
“The cofferdams are hiding the hard work that’s been going on and once they’re all removed, we’ll be able to see the bridge with its beautiful curvature across the harbour taking shape.”
Each pier is constructed inside a cofferdam, which is a watertight box made from joined-up steel plates or ‘sheet piles’ driven up to 20m below the seabed and rising above the water level at high tide. Once the cofferdam is in place, the seawater is pumped out and the floor area inside the cofferdam is excavated down to solid rock. A concrete floor is then laid as the foundation for construction of each pier.
The new bridge will be completed in 2022 and restore the vital walking, cycling and fishing connection to the Māngere Bridge and Onehunga communities.
As well as connecting to Auckland’s wider cycling network, the new bridge will provide increased clearance underneath and space between the piers for waka, canoes and small watercrafts to travel into the Māngere Inlet.
For more on the project, go to https://www.nzta.govt.nz/projects/old-mangere-bridge-replacement-project
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