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The Green Party says sewage from an overflowing Horowhenua treatment plant has spilled into Lake Horowhenua.
Greens co-leader Russel Norman today released aerial photos that showed the pond's contents spilling across a paddock towards the lake, where a dirtier plume of water was visible.
Dr Norman said that was caused by groundwater seeping into the lake. That was occurring because the only thing between the contents of the pond and the lake was now unlined earth banks.
He called on Horowhenua Mayor Brendan Duffy to take action or resign.
"This is turning out to be one of New Zealand's worst sewage disasters in years, yet Horowhenua Mayor Brendan Duffy is still in denial."
Dr Norman said the two lined ponds at the plant had overflowed into two unlined depressions creating one big sewage lake that itself had overflowed into operating sections of the plant.
The council had tried to contain the overflow with an unlined bund, but it had been insufficient meaning another paddock was being bunded.
He said the council had a poor record on environmental matters and needed to urgently seek outside help.
But Mr Duffy said the overflow was being caused by factors outside the council's control - abnormally high ground water levels caused by heavy rain.
The council was doing all it could to mitigate the problem.
The plant was continuing to work, but was struggling to pump out the high volumes of excess water fast enough.
In relation to Dr Norman's call for him to resign, he said the Greens co-leader should "grow up".
"We've taken every possible action on this. It is nature challenging us to the limit," he said.
"We have invited him up to show him what we are doing and the invitation still stands."
- NZPA
