A review has found years of governance failures, historical underinvestment and fragmented accountability caused the flooding that pumped billions of litres of untreated wastewater into Cook Strait, writes Henry Oliver in today’s excerpt from The Bulletin.

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A review into the failure of Wellington’s Moa Point sewage treatment plant has found the disaster was not the result of a single decision but the “cumulative effect of longstanding weaknesses in asset stewardship, risk management, accountability, governance, and infrastructure resilience,” the Herald’s Ethan Manera reported yesterday.

Seven months after the plant flooded in February, pumping around 14bn litres of raw sewage into the ocean, the review has laid bare a litany of failures by Wellington City Council, Wellington Water (now Tiaki Wai), and plant operator Veolia.

“The flooding event was not the result of a single decision or isolated failure,” the report said, according to 1News. “While the governance model remains sound in principle, in practice it has drifted, creating gaps in stewardship, accountability, and risk management that have compounded over time.”

A disaster waiting to happen

The review, led by water infrastructure expert Raveen Jaduram, found the plant was not built to its intended capacity when commissioned in 1998. By 2018, it was showing signs of deterioration and deferred maintenance. By 2021, it was consistently assessed as performing at a “poor” level, the Herald reported.

The report highlighted a “long history of fragmented operational arrangements” and a “pattern of structural underinvestment” in water assets, blaming concerns over affordability and underspending in capital programmes. There was a lack of risk oversight, with the council receiving only high-level information.

Local government minister Simon Watts said multiple parties were to blame for the “completely unacceptable” disaster, the Herald reported. “We need to do everything we can across the broader system to just avoid this type of incident ever happening again.”

What happened on the night

Late on February 3, the plant was operating under “constrained conditions” due to upgrade work on a disinfection unit. The review found limited evidence that operations were adjusted to manage this risk, with no planned contingency or changes to staffing, RNZ reported.

A major rainfall pushed wastewater flows beyond capacity, forcing it back into the plant. An earlier report found a design fault trapped air in the pipe, causing the blockage that flooded the plant with raw sewage.

The facility wasn’t staffed on the night beyond an on-call duty operator and a duty manager. When alarms were triggered, they were not sent to staff. It took 50 minutes for the duty manager to arrive, and nearly another hour before pumps were isolated.

‘Probably could have been avoided’

Jaduram told RNZ the failures to “doing heart surgery on a patient without a full appreciation of the risks” – a risk analysis was done for a UV upgrade project, but not for the whole plant as a system. “The most concerning aspect was that this probably could have been avoided,” Jaduram said. “No one seemed to have the total overview of this project, while the plant is operating.”

Flooding events in July 2025 and January 2025 were not picked up as crucial warnings, the review found.

Recommendations and response

The review made six recommendations, including requiring Tiaki Wai to commit to a remediation plan, upgrade plant capacity and operations, and strengthen incident management, 1News reported.

Wellington mayor Andrew Little apologised to South Coast residents, telling the Herald: “I am very sorry that this has happened. It is our job to make sure, having been told what the flaws were over the last few years or many years, that we respond effectively to it.” Little accepted the disaster was “preventable and avoidable” and spoke of a concerning acceptance of inadequacy among the organisations, RNZ reported.

Tiaki Wai board chair Will Peet said the failure was “devastating” but that staff were on track to fix the plant so it is treating sewage by November this year, but, the review also noted that key Wellington City Council infrastructure leaders did not front up to discuss the terms of reference, the Herald reported.

Another report commissioned by Wellington Water has not been released, with Little saying insurers were “insistent it’s not disclosed,” but that he was keen for it to be shared.