A new plan has been hatched to try to resolve a years-long fight to protect native fish at Transmission Gully.
The Greater Wellington Regional Council has been fighting the builders of the motorway north of Wellington.
It says some of the nine consent breaches it has alleged remain outstanding - most to do with fish having trouble getting around, or sediment runoff into a very sensitive inlet.
They have now agreed on a new plan, with the NZ Transport Agency taking over responsibility for operating the highway for the first time.
It had been done under a public-private partnership (PPP) with the Wellington Gateway Partnership (WGP).
The change follows a confidential settlement of High Court action announced this week that benefits NZTA by several million dollars, but leaves it having to pick up the maintenance and operations that the PPP was meant to take care of.
"The relationship between NZTA, the Wellington Gateway Partnership and project builders has created challenges for Greater Wellington as the regulator," said council chair Daran Ponter.
Regulating it had cost about $7 million over the years, which it had sought to recover, the council said earlier.
When RNZ asked several months ago which entity the council was pursuing over the consents, it initially refused to say.
WGP disavowed responsibility, which angered local iwi.
Greater Wellington later dismissed charges lodged in the Environment Court against the builders CPB HEB Joint Venture, based on legal advice it could achieve more by getting an enforcement order.
"Since then, we have been working with the parties involved to address compliance with outstanding consent requirements, which has resulted in an agreed action plan," Ponter told RNZ.
They might make the plan public, and "meantime, we can reveal that work required by the action plan is underway, including steps to address fish passage issues".
The project's impact on streams and diversions, and maintenance of planting, had been other problems.
NZTA told RNZ that the post-settlement change meant its relationship would be more direct with the council, as it takes on the job of fixing what it says were remediation jobs left undone along the motorway, which might take a couple of years.
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