Another piece of the stormwater puzzle arrives in Auckland

Publish Date : 02 Feb 2021
Another piece of the stormwater puzzle arrives in Auckland

Have you been wondering what the boat trailing the long black tail, moored off the Westhaven Marina breakwater is?

No, it’s not anything to do with the America's Cup.

Rather it’s part of the St Marys Bay Area Water Quality Improvement project which reached a major milestone with the arrival of a 460m long marine outlet pipe, towed from the Firth of Thames to the Waitematā Harbour.

The project is part of a coordinated suite of wastewater and stormwater upgrades designed to dramatically reduce overflows into the Waitematā Harbour and clean up Auckland’s inner-city beaches, making them safer more often, for swimming.

Auckland Mayor Phil Goff says, “We’re investing almost $2 billion to clean up our beaches and improve water quality in our harbours and waterways, with this investment enabling us to achieve the critical infrastructure upgrades required to reduce wastewater overflows 20 years faster than had previously been planned.

“The St Marys Bay Water Quality Improvement project will reduce wet weather overflows at Masefield Beach and St Marys Bay from approximately 100 per year to less than 20, with further improvements once the wastewater network is separated from the stormwater network.”

The HDPE pipe, manufactured in Thailand and assembled in Kaiaua, travelled the 62km behind a tugboat and is now temporarily moored off Westhaven Marina while concrete ballast blocks are fitted. It will then be moved into position and carefully sunk into a dredged trench to form the outlet for the new stormwater tunnel which has been tunnelled beneath St Marys Bay, from London and New Streets to Point Erin Park.

“It was a challenge in logistics to bring a pipe this long into a busy harbour amidst the Americas Cup. We had to work closely with the Harbourmaster to schedule its arrival and brought it in overnight to avoid marine traffic,” says Project Manager Stephen Scard.

“The system to attach the ballast blocks has also been specifically designed for this project so they can be fitted on water. Due to the large size of the pipe, lifting it out of the water to install the concrete blocks was not an option as it could bend and damage the pipe,” he adds.

The project has been under construction by Auckland Council and contractor McConnell Dowell since January 2020 as part of the greater Western Isthmus Water Quality Improvement Project funded by the Water Quality Targeted Rate.

“We want to restore these beaches to being thriving, lively places where people come together to enjoy themselves,” says Healthy Waters General Manager Craig McIlroy.

“We estimate that when our project is complete, St Marys Bay will be able to be used safely at least 95 per cent of the time by all water enthusiasts including swimmers, children learning to sail and dragon boaters.”

While the stormwater pipe construction will complete in mid-2021, Watercare is also working to separate the local wastewater and stormwater pipes, leading to even greater reductions in overflows and further enhancing St Marys Bay water quality.

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