New Wastewater Storage Facility a major win for Porirua

The health of the Porirua Harbour will be materially improved thanks to the Porirua Central Wastewater Storage Facility, which was officially opened today by Porirua City Council and Wellington Water. 

“Wellington Water has delivered this project on behalf of Porirua City Council to manage the pressure that is placed on the network when it rains heavily, resulting in wastewater overflows into streams and Te Awarua o Porirua – Porirua Harbour,” says Wellington Water Board Chair Bill Bayfield.

“A key feature of the new facility is the storage tank, which can hold up to seven million litres of wastewater. The wastewater can then be gradually released back into the network for treatment at the Porirua Wastewater Treatment Plant. During heavy rain, this will significantly reduce the volume and number of untreated wastewater overflows into our natural environment.”  

The Porirua Central Wastewater Storage Facility is a key project supporting the objectives of the Porirua Harbour Accord, which Wellington Water and Porirua City Council signed alongside partner organisations in 2025. 

Porirua Mayor Anita Baker says “the health of Porirua Harbour has been a long-standing priority for the Council and for our community. Based on historic overflow data between 2017 and 2024, the facility is expected to reduce wastewater entering Porirua Stream and Porirua Harbour by an average of 26,000 cubic metres each year – the equivalent of approximately 10 Olympic-sized swimming pools.” 

“This is a huge environmental win for Porirua and a major investment in protecting the health of our waterways and harbour, particularly as our city continues to grow and severe weather events become more frequent”, she adds.  

The completed storage tank can hold seven million litres of wastewater, while the accompanying pump station contains two pumps capable of moving up to 700 litres of wastewater per second.  

Construction of the project began in 2022. Despite the complexity of the works, including the successful relocation of protected northern grass skinks from the construction site, the project was completed in May 2026, two months ahead of schedule.

“The new facility has already proven its value,” says Bill.  

On 18 May, a burst water pipe in Porirua City Centre required flows to be diverted away from the worksite to allow for urgent repairs. Prior to the completion of the storage facility, this would likely have resulted in wastewater being discharged into the harbour while repairs were undertaken.

Instead, wastewater was diverted into the storage tank and later pumped back into the network for treatment once repairs were completed. 

“The successful use of the facility during this repair provided an immediate demonstration of the benefits it will deliver for Porirua and the harbour environment for years to come,” says Bill.