Confusion over who is responsible for Transmission Gully's environmental impacts

A landmark Wellington motorway once lauded for its green credentials is being investigated for its impact on streams, native fish and one of the country's most sensitive inlets.

Newly released information shows Transmission Gully's problems have persisted since its opening early last year.

It was built as a public-private partnership and is being operated by a consortium of financiers and contractors. But project partners, including Waka Kotahi, are caught up in court action and it is not clear who might be held accountable.

The road's green certification was trumpeted early on. However, it went on to cop a host of environmental sanctions and over $110,000 in fines during construction.

The Greater Wellington Regional Council has now revealed to RNZ it is investigating nine possible breaches of resource consent conditions, including high levels of sediment getting into Pāuatahanui Inlet, which has been silting up at five times the natural rate.

Fill has been dumped into three kilometres of a stream without a consent. "The stream's flowing channel has been diverted," a council summary said.

And fish migrations may be being blocked - but there is a dearth of the supposedly mandatory reports to be able to tell.

The council would not identify what entity it is investigating, and Waka Kotahi was tightlipped because of its legal fight with the builder: "Because many of the matters you have asked about are directly related to ongoing legal action, we cannot provide further comment."

Local conservationists were in the dark. Porirua iwi Ngāti Toa, which named parts of the motorway, said it needed to know more but "first and foremost, we're incredibly disappointed".

The public-private partnership (PPP) approach was favoured by the incoming government to pay for roads and big infrastructure projects, according to its election campaign policies.

The Wellington Gateway Partnership (WGP) built the road and has a 25-year contract to operate it, while it remains in public ownership.

"No, Wellington Gateway Partnership is not responsible for the environment controls and management employed on this project," a spokesperson told RNZ.

Another firm, Ventia, holds the motorway operations and maintenance contract with WGP. Ventia's website said this covered "environmental management".

But the company said it was "not responsible for this work", and referred RNZ's queries to WGP.

On Thursday morning, it added that "Ventia's responsibility for environmental management activities commences upon completion of the motorway".

Regional councillor for Porirua Hikitia Ropata said the contracts were "pretty clear" about this.

"I'm saying it's disappointing that nobody's put their hands up for the accountability of that," she said today.

"We don't go into these negotiations or the care of our environment naively, so I would have expected that actually companies are able to put their hand up and say, 'Yeah, we got this wrong'."

The regional council also declined to specify just what it is doing with its arsenal of enforcement tools.

It was "working through this issue (including in discussion with the project) to determine an appropriate way for this issue to be addressed", it said on eight separate occasions in a three-page summary released to RNZ.

It dropped Environment Court charges in August against the construction joint venture - CPB HEB Joint Venture - on legal advice that it was better off pursuing an enforcement order, it said on Wednesday.

It conducted inspections at the motorway in September. Its summary said:

[LIThree kilometres of stream in Horokiri catchment next to the road was diverted without consent. "An application for consent to authorise this work was made by NZTA and was withdrawn in September 2023."

• Some streams, culverts and diversions were reinstated or built wrong, lacked ecologist or engineer sign-off, or might pose barriers to native fish migrating.
• For sediment that posed a threat to the inlet, "there have been trigger breaches between 2016 and 2023" (this was meant to trigger an investigation).

Most stormwater treatment devices had been installed correctly, except the one at Waitangirua wetland.

The motorway, as well as subdivisions, farming and forestry are known to be silting up inlets, the only large coastal wetlands left in the lower North Island.

Ngāti Toa Rangatira said it was "incredibly concerned if that is the case" about breaches.

"Without knowing the scale of these, it's hard to ascertain or determine what the potential impact of these are," said Rawiri Faulkner, the pou toa matarau or leader of environment, settlements and culture for Te Runanga o Toa Rangatira.

"But minor or major... they're all important to us."

He would ask the council for details.

The council said it could not say much about when enforcement might be needed, but would talk to the iwi when it could. It added that the iwi's views were incorporated early into the resource consents for the road, and it was investigating now to "retain the integrity of the consents".

Years ago, Waka Kotahi heralded Transmission Gully for achieving 'Greenroads' silver certification standard, and for its PPP approach - the first for a road - saving taxpayers $25m in build costs.

It ultimately probably doubled its $700-800m budget, stretches have already needed resealing, and a legal fight continues over whether it is finished or not.

A council spreadsheet released to RNZ showed in one particularly bad patch, in May 2019, the project was hit with nine infringement notices after stormwater defences slumped or overflowed, with dirty water rushing into the Horokiri and other streams.

A local residents group concerned about traffic noise, and a conservation group worried that works on the flood plain at Lanes Flat have not been finished, told RNZ they knew little about any breaches but wanted to know more.

PPPs had a very mixed track record globally. Lawyers Chapman Tripp have noted that New Zealand needed to "come up to speed" on them since the incoming government would likely use them more.

The Gully PPP has been riven by costly, messy legal disputes between the partners. The builder, CPB HEB JV, is suing Waka Kotahi over its insistence the job has not been completed properly.

"Waka Kotahi is focused on achieving compliance with and completing outstanding consenting requirements," the agency told RNZ. "We are communicating with the Greater Wellington Regional Council about the project's compliance."

A few years ago the agency said: "Achieving good long-term environmental outcomes is a big part of Transmission Gully's new motorway."