Wellington sewage spill: Extent of damage to Moa Point plant revealed
Thursday, 2 April 2026
The “heart and nervous system” of the Moa Point sewage treatment plant was damaged in a catastrophe which continues to see untreated wastewater discharged off Wellington’s south coast almost two months on.
Wellington Water on Wednesday night released details of some of the damage from the February 4 incident showing the extent of the damage meant 14.5km of cables in the plant would need to be repaired or replaced.
The formal assessment was done for insurance and would be made public “as soon as appropriate” – though this may be after a review for any potential insurance claims.
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There was damage to “critical mechanical equipment including the odour treatment, sludge pumping and aeration equipment”, a statement from the utility said.
Electrical damage included the Programmable Logic Controller, Motor Control Centre, control instruments and cabling, which were “essentially the heart and nervous system of the treatment plant”.
The Moa Point sewage treatment plant on Wellington’s south coast failed on February 4. The plant was extensively damaged and 70 million litres of untreated wastewater daily has been discharged off the south coast, near the entrance of Lyall Bay, since.
An earlier hydraulic report into the disaster found trapped air and a series of events led to the fiasco.
Nobody was on-site overnight when heavy rainfall sent a deluge of rain and wastewater to the plant, which was being monitored remotely.
It came as maintenance work was being done, meaning waste was taking a different route though the plant – one that stirred bubbles into the mixture creating a blockage, which caused a back-flood of sewage and water to inundate the plant instead of sending it down a 1.8km pipe to Cook Strait.
With no person on-site, which was operating practice for the plant, the waste could not be sent down another outfall and it instead flooded the plant, causing extensive damage.