Wastewater overflows at Mairangi Bay will be few and far between thanks to a new $22.5 million wastewater pump station now in service.
Project manager Dirk Du Plessis says the new Mairangi Bay wastewater pump station can handle flows of up to 625 litres per second – double that of the old pump station now being demolished on Sidmouth Street.
“The increased pumping capacity and the pump station’s integrated storage wet well of 230,000 litres will play a major role in significantly reducing the number of wet weather overflows; helping to protect inlets, reserves and beaches for today’s and future generations to enjoy.
"It replaces the old 60-year-old pump station in Sidmouth Street that had come to the end of its design life.
“Due to the steady rise in population growth, the old pump station was struggling to keep up with demand during heavy rainfall.”
As a result, wet weather overflows occurred at Mairangi Bay up to 10 times a year – with wastewater being discharged into the sea at engineered overflow points at both sides of the beach.
Du Plessis says the $22.5m pump station – built by construction partner Pipeline & Civil – will be highly resilient in severe weather events and will significantly reduce the number of overflows.
“The pump station is fully automated and equipped with four submersible pumps mounted in a drywell.
“This means in an extreme weather event the pumps will keep pumping wastewater even if the pump chamber gets flooded.
“Even if initial power goes out, another power source will kick in as the pump station is fed through two separate power sources.
“One to two pumps will usually be in operation with a third pump to assist. The fourth pump will be on standby mode in case there is any failure.
“Also, the pump station has a state-of-the-art odour control unit to eliminate bad odour that comes from the wastewater.”
Project manager Dirk Du Plessis stands next to the wastewater pump station’s four submersible pumps 12 metres below ground
Du Plessis says the pump station's construction was challenging, particularly in the initial stages when the project started in June 2021.
“The pandemic certainly caused delays, with problems getting the people and materials for the job.
“Constructing the wastewater pump station beside Mairangi Bay beach was also particularly challenging for us because there was only one access point. Since construction works could be done from only one side, we could only do one activity at a time.
“Given the pump station’s proximity to the beach and limited access points, we had to build it from the bottom up using a crane. Unfortunately, high winds and storms prevented the construction team from working with the tower crane on 53 days, which further delayed the project.”
Du Plessis says the Mairangi Bay Pump Station will connect in with the $21.5m East Coast Bays Pipeline which is on track to be completed mid-May.
The East Coast Bays wastewater pipeline is on track to be completed by mid-May
“Alongside the new Mairangi Bay Pump Station, the wastewater pipeline will increase the wastewater transmission capacity and further reduce wet-weather overflows in the East Coast Bays area.
“The new pipeline will be able to carry large volumes of wastewater pumped out at the new Mairangi Bay pump station all the way to our Rosedale Wastewater Treatment Plant.”
“The completion of these two projects marks the end of a major two-and-a-half-year journey that will not only improve the outcomes for the community and the environment, but also frees us up to pursue new infrastructure projects that further benefit the community.”
Du Plessis thanks the community for their understanding, support and patience as Watercare worked to complete both projects.
“Although this project has been particularly disruptive at times, the support and interest we’ve received from the community has been great.
“Most residents, businesses and commuters have stood by us as they well understood the community and environmental benefits of these critical infrastructure projects.”