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The catastrophic failure of the Moa Point wastewater treatment plant was caused by long-standing systemic failures of leadership by Wellington City Council, Wellington Water and the plant's operator Veolia, a damning report has found.
The plant, which flooded and shut down on February 4, has by now spewed approximately 14 billion litres of raw sewage into Wellington's south coast - pumping the waste close to the shore at Tarakena Bay after a heavy rain.
Some residents have stopped fishing, diving and swimming at the beaches regularly, while businesses have said they've been forced to the brink of closure due to the disaster.
While the report from the Crown Review team did not point to a single decision or event, it said the failure reflected "systemic governance failure" in how the treatment plant was managed.
Six recommendations were made, including improving communication and strengthening governance.
However, it paints a picture of a complicated management system where no single organisation acted as though it was in charge - and communication between Wellington City Council and Wellington Water was poor.
Six recommendations were made, including restoring compliance with consents, public communication, and improving risk management.
Wellington City Council, as the plant's owner and consent holder, "remained ultimately accountable" at the time of the incident.
The council maintained to the Crown Review team that it did not control the plant, the review team said.
"WCC relied on Wellington Water to notify it of issues or need for renewals, rather than define standards itself."
Wellington Water, in turn, did not have a detailed management plan for the plant, and no funding plan.
This meant Wellington Water did not make enough funding requests to the council.
Communication between the organisations was poor, the report said.
"Information flows between organisations were indirect and, at times, filtered."
Despite featuring heavily during the investigation, the review team noted that city council infrastructure leaders didn't meet the Crown Review to tell them about aspects of their role as owner of the plant - instead providing written submissions.
The report said this was despite requests for in-person meetings being made.
Crucial warnings missed, no staffing at the plant
The report explained, as a Wellington Review found in March, that during heavy rain trapped air in the plant's sewage bypass pipe caused wastewater to back up, flooding critical electrical equipment and the plant.
It said much more wastewater was being sent through the bypass because work was being done on the plant's UV disinfection system.
The report said Veolia told the Crown Review team it had warned about the bypass pipe risks, but Wellington Water said it was not aware this warning had been made.
An overflow event happened at 3pm on the afternoon before the major flooding event occurred, but the report said Veolia took no additional actions.
A flooding event in July 2025 showed similar warning signs, the report said. The Crown Review team said Wellington Water was not aware this was raised by the operator.
There were also no staff on site at the plant - Veolia stated they were not instructed to increase monitoring or staffing with the UV system under upgrade.
No extra staff were required overnight as the conditions were considered typical.
Minister and organisations respond
Local Government Minister Simon Watts said the public deserved answers over what happened.
"The failure of the Moa Point Plant was one of the most significant wastewater infrastructure failures experienced in the Wellington region in recent decades."
He said lessons from the incident could strengthen management in the future.
"The review found the event was not caused by a single decision or isolated failure, but by longstanding weaknesses in governance, accountability, asset management, risk management and infrastructure resilience.
"The review's central finding is that preventing a similar event in the future depends on clear accountability throughout the system, supported by a strong understanding of risks and effective decision-making at every level.
Wellington Mayor Andrew Little said the Crown Review team report into the failure of the Moa Point wastewater treatment plant in February was thorough.
"What happened at Moa Point is unacceptable. The bottom line is Wellingtonians deserve transparency, and to have assurance about the response and recovery. That is why I asked the central government to commission a suitably independent report," Little said.
"On behalf of Wellington City Council, I acknowledge and accept the report's findings."
Tiaki Wai, now owner of the water assets, said it welcomed the report.
Board Chair Will Peet said: "The failure of the plant on 4 February was devastating. As a south coast resident and frequent visitor of the affected beaches, I was as upset as many fellow Wellingtonians. We know that local residents, the business community and mana whenua have felt this very deeply."
He said Tiaki Wai was focused on fixing the plant.
