Safe swimming in the bays – Mairangi Bay Pump Station

Civil EngineeringSurveyingPlanningThree Waters

Swimming in the bays along Mairangi, Long and Castor Bay in Tāmaki Makaurau after heavy rainfall has long been a big ‘no no’. The old pump station couldn’t cope with the influx of new homes in the area and sometimes diluted wastewater would overflow out at sea. We recently spoke with our National Infrastructure Manager, Steve Jones, about how Harrison Grierson led the design team to create an award-winning pump station for generations of people to enjoy the ocean once more.

Auckland is renowned for its aging infrastructure. Beaches often feature ‘do not swim’ signs due to heavy rainfall and failing wastewater pumps. 

The pump station at Mairangi Bay was built in 1962 and at the time only serviced about 50,000 homes and facilities. Fast forward 60-plus years and the same pump station just couldn’t cope.

Pipeline and Civil had won the work from Watercare to replace the station and needed a design partner to optimise their plans who specialised in three waters.

We joined the project team in 2021 and quickly began figuring out how to keep the existing pump station operating while building a new one next door which was sitting on a rigid 11m-deep, lined secant-piled shaft and soft soils.

We designed the new pump station building as a precast panel solution off-site rather than in situ to speed up delivery and increase build quality.

‘’We also had to design a massive 600mm thick, cantilevered slab to hold up the building given the foundation issues and the close proximity of several protected trees. It was a real design challenge which the team relished,’’ says Steve.

Throughout the design process, we used 3D software Revit, Navisworks, Civil 3D and Inventor to make sure the congested shaft and building didn’t clash and to prevent any on-site rework.

We increased the capacity from about 300l/s to 625l/s and added additional storage to mitigate emergency overflows.

‘’We’re delighted to see people swimming safely in the bays again’’.

The Mairangi Bay Pump Station was awarded gold at the Auckland CCNZ HYNDS Construction Awards in November 2023.