Transmission Gully is go, with opponents conceding defeat in their battle against the $930 million highway.
An independent board of inquiry yesterday granted consent for the new inland highway, which will shave 10 minutes off motorists' peak-time journeys between Kapiti and Wellington.
It means the project, first mooted almost a century ago, has no more bureaucratic hurdles to cross with opponents confirming they have no plans to lodge appeals.
Only an appeal to the High Court could stop it now, though detractors say funding may yet fall through.
The announcement sparked widespread joy from proponents of the "crucial" four-lane highway but resignation from opponents, who say the battle is over.
It will see a 27km inland highway cut through the hills from Linden to rejoin State Highway 1 north of Paekakariki, securing a vital arterial route and reducing congestion for frustrated commuters.
The NZ Transport Agency expects to begin construction in 2015 and have it completed by 2021.
State highway manager Rod James said consent gave certainty to the project and "extensive safeguards" would mitigate the project's environmental impact.
"The regional benefits include support for a growing population and increasing freight volumes, improved access to Wellington's port, the CBD, Wellington Airport and Wellington Hospital, relief from traffic congestion and improved road safety ..."
It will be one of New Zealand's biggest infrastructure projects and the Wellington region's biggest roading project since the Wellington motorway extension in the late 1970s.
Green Party transport spokeswoman Julie Anne Genter said the party lacked resources to appeal but would support any group that did.
She expected the Government would run into funding problems for the project.
Arabian stud farm owner Eberhard Deuss joined forces with his neighbours to fight for a section of the highway to be pushed back 150 metres from their Paekakariki Hill Road properties.
He would "not waste any more time" with further appeals.
"It was a fait accompli ... I'm just the little guy so I don't get a say."
Coastal Highway Group spokesman Dick Jessup, a 12-year opponent, said an appeal would be too expensive and "unlikely".
"There's nothing to stop it now."
Rational Transport Society spokesman Kent Duston would not appeal because the only avenue was arguing whether due process had been followed.
Sediment runoff into Pauatahanui Inlet was a key concern for opponents.
But Forest & Bird North Island conservation manager Mark Bellingham said planned remedial work would actually improve the environmental status of the catchment.
UnitedFuture leader Peter Dunne said the new route was "crucial" to give people access in and out of Wellington.
"It has been a long battle but frankly, this is the only decision that ever made sense and it had to come."
Greater Wellington regional council chairwoman Fran Wilde said the decision was "great" news and would take pressure off the existing route, which carried 13,000 vehicles each day.
"The new Transmission Gully route – which has higher seismic resilience than the present route – will help to future-proof our region.
"This is not only the main highway between Kapiti and Wellington – and all the communities in between – but it is the main route for freight from the top of the North Island into the South Island. In economic terms New Zealand cannot afford to have such an unreliable stretch of road."
Transport Minister Gerry Brownlee applauded the decision, saying the highway – one of seven roads of national significance – was "now set to become a reality".
Porirua Deputy Mayor Liz Kelly was `absolutely delighted" but acknowledged concerns about damage to "our priceless Pauatahanui Inlet". She believed consent conditions would mitigate potential harm.
Wellington Civil Defence regional manager Bruce Pepperell said it would be an "escape route" in an emergency.
"It's more than that. Anyone who lives down here understands that access is restricted at critical points. It doesn't take a significant earthquake to do this, it just takes a simple storm and a slip to cut the area off."
Last month the board of inquiry gave provisional consent for the road but sought feedback before yesterday's final decision. No major changes were made to the provisional consent.
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