Preventing overflows in Auckland with Watercare

The utility company has spent more than $40 million to prevent overflows in Auckland’s East Coast Bays in the past few weeks.

Wastewater overflows at Mairangi Bay will be few and far between thanks to a new $22.5 million wastewater pump station now in service.

Watercare project manager Dirk Du Plessis said 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.

According to him, the new Mairangi Bay wastewater pump station could handle flows of up to 625l 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,” he said.

“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 said 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,” he said.

“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.”

According to Du Plessis, one to two pumps will usually be in operation with a third pump to assist. The fourth pump is set to 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,” he said.

Du Plessis said 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,” Du Plessis said.

“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.”