Preferred Petone to Grenada route would affect 85 houses

Tuesday, 3 February 2026

It might have the best value for money and could shave off the most driving time between Lower Hutt and Porirua, but the proposed route between Petone and Grenada would affect about 85 houses and pose a greater ecological impact on native bush than the alternatives.

NZ Transport Agency Waka Kotahi released the full investment case for the 5.5km four-lane highway in Wellington’s northern suburbs on Friday, showing it considered a four-option short-list for the road’s design.

That included the agency’s preferred course of passing Horokiwi from the intersection with Cross Valley Link on Hutt Rd, a 410-metre tunnel under Woodridge, another 230m tunnel under Mark Ave and ending at Grenada Drive, traversing through two reserves, the Gilberd Bush Reserve and Seton Nossiter Park.

It skirted the Lincolnshire Farms development, where 2500 new houses would be built over the next 30 years, instead of cutting across the area like the three other short-listed options, including its preferred design back in 2015.

Read More:

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• More details of new SH1 Wellington route revealed - and the houses affected

• Saving minutes, spending billions: Checking the big claims behind Wellington highway push

• Wellington City Council blasts ‘critical information gaps’ in NZTA SH1 plans

The investment case suggested NZTA’s preferred route would affect about 85 houses, of which about 40 were located above the two tunnels. That was fewer than the 450 affected properties in the 2015 design but more than the 35 properties in the two alternatives that span Lincolnshire Farms.

From the short-list, the selected route had the “greatest ecological impacts on indigenous vegetation” and “moderate direct impact” on the Belmont Stream, a tributary that flows into the Porirua Stream.

Officials picked that design because it was less steep, could cut the most driving time between Lower Hutt and Porirua by 15 to 20 minutes, had the “least impact on housing growth areas”, and being the second cheapest option – made slightly more expensive because of the tunnels – was the best value for money.

That route was also forecast to divert the most traffic from the state highways, cutting down congestion at the Ngauranga interchange.

“While the option has notable ecological impacts, these are expected to be mitigated or offset appropriately,” said the investment case, without elaborating.

Peter Gilberd, a former Wellington City councillor who leads community planting group Woodridge Planters, called NZTA’s route choice “extremely poor” and “unnecessary”. The group planted native trees in reserves around Newlands and Paparangi, including Seton Nossiter Park and Gilberd Bush Reserve.

Both reserves had highly developed ecological systems with “extremely valuable” trees, including 800 northern rātā at Seton Nossiter Park, he said.

“Once you destroy the bush, you destroy it forever.”

The investment case’s entire tolling assessment, funding details and large swathes of costing information were redacted, but it estimated Petone to Grenada’s cost per kilometre would be more expensive than Transmission Gully because of “project complexity, terrain and earthworks disposal”.

It offered no particulars on timelines, only saying the project planned to submit resource consent application under the Fast-track Approval Act and start property acquisition this year.

The Wellington City Council made a submission to NZTA about its plan for two new tunnels under The Terrace and Mt Victoria, criticising the “critical information gaps” on detailed layouts, intersection designs and signal phasings.

A council spokesperson said it was too early to make a call if it would do something similar with the Petone to Grenada road: “We may make a submission if NZTA call for public feedback similar to SH1.”

An NZTA spokesperson said in late January the project was in a “route protection” phase and the agency was running ground and environmental investigations to understand soil, land, and environmental conditions along the preferred route. There would be information sessions this year to “share updates” and answer questions.

Residents living along the preferred route previously told Local Democracy Reporting they were concerned about the project’s minimal details, the unclear environmental and noise impacts and what they say was inadequate public input.

Having been stuck on the planning table for years, the Petone to Grenada road was costed at $270 million and looked it could begin construction in 2019 but it was pushed back that same year.

Local Democracy Reporting (LDR) is local body journalism co-funded by RNZ and NZ On Air