Kim Baker Wilson,

A new wastewater plant north of Auckland will go a long way to almost stopping sewage overflows in wet weather that have devastated local oyster farmers, Watercare says.

The plant at Snells Beach officially opened on Monday and was attended by staff who had worked on it for years to notch up 500,000 hours worked.

Auckland mayor Wayne Brown and Building and Construction Minister Chris Penk were also there.

"We'll have the capacity to put more people into the community," Watercare chief executive Jamie Sinclair said.

Watercare chief executive Jamie Sinclair. Photo: RNZ / Kim Baker Wilson

It was already now thousands more, with the new treatment plant able to handle wastewater from 18,000 additional people.

The plant was designed so it could cope with growth for the next 35 years.

It was handling more than half of Warkworth's waste now, and would treat all of it when the commissioning process was over.

Snells Beach Wasterwater Treatment Plant. Photo: RNZ / Kim Baker Wilson

Project manager Casper Kruger said the plant was ready now for expansion in the years to come.

"It's a complete change in approach as far as quality is concerned, this can do far better quality of wastewater and too a much larger scale," he said

But down the road at Matakana Oysters, Tom Walters said oyster farmers were still facing profound uncertainty after the rolling sewage overflows.

"It's great that it's up and running and looking very shiny and new but it's not in the river and our livelihoods," he said.

Tom Walters inside Matakana Oysters. Photo: RNZ / Kim Baker Wilson

The full fix that Watercare said would almost completely cut sewage overflows when it rained was still some time off.

The final part of the $450 million programme, a growth servicing pipeline, was in design and would have construction begin next year.

"You can't sleep at night when you hear rain on the roof because you know that it is going to bring sewage," Walters said.

"We're still not out of the woods.

"A lot of us have used every single last cent that we've had to keep going, to keep the lights on. I had a home once, I've had to put that up for sale," Walters said.

"Financially we're all just completely ruined."

Watercare chief executive Jamie Sinclair, when asked if it would consider compensation, said the agency would continue talking about what support it could give.

The new plant. Photo: RNZ / Kim Baker Wilson

This story was originally published by RNZ