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Big milestone in Wastewater Treatment Plant upgrade

Monday 6 December 2021

An enormous concrete pour early this morning was a big milestone for the Wastewater Treatment Plant (WWTP) upgrade on Banks Street.

The $34.6 million project will double the size of our existing WWTP and is being built on the site next door.

Council Lifelines’ Director Dave Wilson says once finished it will treat our wastewater with state-of-the-art technology to make it even cleaner before it’s released into our Bay.

For the past few months Council has been working hand in hand with world-renowned construction specialists McConnell Dowell Constructors Ltd.

This morning, 25 truck-loads of concrete were delivered to the Banks Street site, which will form a 140 tonne, 8m by 8m by 6m deep Pump Station Base, and wall slabs.

To put the size of this project into context, for the ground improvements 60 per cent of the North Island’s weekly cement use is coming to the Banks Street site for the next six weeks.

Mr Wilson says it’s one of the biggest projects Council is working on.

“When this is finished our wastewater will pass through a lamella clarifier, filtration, ultra-violet disinfection, and sludge handling facilities to treat household wastewater.

“Council’s 10-year plan also includes a wetland area, where our wastewater will be filtered through a natural disinfectant process to keep it out of our waterways.”

Principal Contractor McConnell Dowell has brought a team of experts from around New Zealand for this project – including site engineer Hayley Scott, recognised this year as an emerging leader in the Civil Contractor NZ (CCNZ) 2021 awards.

McConnell Dowell project manager Phil Terry says his team is almost finished with the underground works ready for Phase Two, which is the above-ground construction starting next year.

Ground improvements have included a large drill, like a food processor in the ground, drilling 6m down while injecting cement grout into the sand base. Once this sets it’s going to be “almost like a limestone block”, says Mr Terry.

There are six clarifiers to be installed that will take 86 days, six contractors, and almost a million bolts to put together.

Mr Terry says making sure this project goes smoothly in a complicated live environment is all about the planning.

All the material dug out of the site is also being trucked to the Kiwa Pools complex, which needs an extra 1.5m of land on site. This is a big cost saving for Council, says Mr Terry, as otherwise, this material would’ve gone to a landfill at a cost.

Phase Two also signals the start of Council’s social procurement policy when up to 40 local people will be hired for the build.

The experience these local contractors will learn on this huge project will then stay in our region, says Mr Wilson. The project is being funded by Council and Government’s Three Waters Reform Programme. The upgrade is expected to be completed by August 2022.

For more information on the Wastewater Treatment Plant.