Moa Point plant won't be fully fixed until next year, officials say

Wellington's Moa Point treatment plant will not be fully fixed until at least a year after it catastrophically failed.

By Ellen O'Dwyer of RNZ

In a timeline released on Wednesday, Wellington Water and Wellington City Council say the wastewater treatment plant is expected to be fully restored by February 2027 - and raw sewage should be able to be treated by November this year.

But the timeline also states "full hydraulic capacity" of the plant's bypass and outfall upgrade won't be complete until late 2027.

The treatment plant on Wellington's South Coast flooded in February - shutting it down, damaging equipment and sending millions of litres of raw sewage into the sea each day through the plant's long outfall pipe, about 1 kilometre offshore.

When it rains heavily, the system cannot cope, and the sewage spills close to the shore at Tarakena Bay, from a secondary pipe used for overflow. This shuts South Coast beaches to swimming, diving and surfing.

A report in April revealed an air bubble may have caused the plant's failure - details of another damage report are set to be released on Wednesday.

The timeline stated that recovery works began in April, and that full power and control systems in the plant, along with ventilation, odour systems, and equipment used for primary treatment, should be fixed by September.

It said all major repair works will be completed by November - and that sewage will be able to pass through the full treatment process by then.

Mayor Andrew Little said in a statement the timeline was a "turning point".

"The failure of the Moa Point Wastewater Treatment Plant has caused massive disruption to people, communities and businesses who are connected to the south coast.

"We know the road ahead to recovery, and local communities, businesses and people who use and enjoy the south coast can at least look forward with a degree of certainty about when the plant will be fully restored."

Wellington Water chief operating officer Charles Barker said they would report against the milestones laid out, so people can hold them to account over the progress.

"A key date for the community to hold us to is November, when major recovery works are expected to be complete and we'll be able to start sending wastewater through full treatment processes.

"Secondary treatment - including biological treatment - will be restarted, which will gradually improve the quality of wastewater being discharged out to Cook Strait."

Barker said teams were trying to fix the plant as soon as possible, but that raw sewage may still be spewed into the sea occasionally after heavy rain, while work was going on.

He said he expected these to "reduce significantly" as the plant pumped more wastewater out the long outfall.

Work was underway to address the trapped air bubble identified in April's hydraulic report, Barker said.

"Teams have already restarted major upgrade projects that were underway before the flooding, including the UV and EIC (electrical, instrumentation and control) upgrades.

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"With equipment already procured or being manufactured, work has been able to resume quickly - putting the recovery months ahead of where it would otherwise be."

An independent Crown review into the failure is also underway, and its final report is expected in August.