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Source: New Zealand Transport Agency

Construction of the new walking, cycling and fishing bridge over the Manukau Harbour is entering a new phase, with Waka Kotahi NZ Transport Agency starting work on the central bridge piers.

The team completed constructing the temporary staging platforms out into the harbour, alongside where the new bridge will be built in mid-July. Demolition of the old bridge is also under way.

Now the construction team is starting work on the cofferdams needed to construct the main structural piers of the new bridge. A total of nine cofferdams will be built, two large ones and seven smaller ones.

Mana whenua, Te Ākitai Waiohua, Ngaati Whanaunga and Ngāti Tamaoho, held a karakia this morning to bless the cofferdams and for the safety of workers.

The cofferdams are temporary structures in the harbour that will go 10 metres down to the seabed, says Waka Kotahi Senior Manager Project Delivery Andrew Thackwray.

“A cofferdam is a watertight box made from joined-up steel plates or ‘sheet piles’, so sea water can be pumped out to create a dry and safe work environment. The cofferdam also protects the surrounding environment from the effects of construction.”  

The two large cofferdams, 25m by 12.5m are where the team will build the two main bridge piers that will support the feature arch span which weighs more than 400 tonnes.

All of the cofferdams, including the seven smaller ones, 13.5m wide and 6.5m long, will be built from steel plates or ‘sheet piles’ made to order for this project.

The steel plates, weighing a total of 550 tonnes, arrived by sea in Auckland in the first week of COVID-19 Alert Level 4, when all non-essential construction sites were shut down. They took up a lot of space on the wharf and a request was made to move them to make room for unloading essential goods.

“Waka Kotahi thanks the team of eight from construction partners McConnell Dowell who were given special permission to work for three days to complete the task under strict hygiene and physical distancing protocols.”

Mr Thackwray says the COVID-19 lockdown has had only a small impact on the project, which is due to be completed in 2022. It was shut down for five weeks under Alert Level 4, but work quickly resumed under Alert Level 3, with best practice health and safety protocols in place to ensure the safety of all workers.

“We were fortunate that the steel required to build the temporary staging as well as the steel required for the replacement bridge itself had either already been delivered to site or was already on the way to New Zealand when the site had to shut down.”

“Now we are working with McConnell Dowell to see where we can make up the lost time. We want to restore the vital walking, cycling and fishing connection to the Māngere Bridge and Onehunga communities as quickly as possible.”

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.

The bridge is the result of several years of work with mana whenua, the community, local boards and other stakeholders to create an architecturally designed structure that will also serve as a community meeting place for years to come.

Old Māngere Bridge Replacement project webpage

Framing for one of the large cofferdams (front right) is taking shape next to the staging platform for construction of the replacement Māngere Bridge.

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