An Environment Court hearing has cleared the way for the new road needed to provide ongoing access to Waiinu Beach settlement.
The road from Nukumaru to Waiinu Beach was proposed by the South Taranaki District Council because the Limeworks Bridge on the settlement's only access road is weak and likely to fail.
"There's nothing surer. It's a matter of when, not if," South Taranaki District Council engineering services manager Brent Manning said.
The new road's route extends existing Nukumaru Station Rd. It was appealed by organic dairy farmer Diana Handley, who stood to lose some land. The matter went to mediation and the amount of land she will lose was reduced from 4.6ha to 2.8ha.
Her appeal was heard in the Environment Court in Whanganui on June 25 and 26. The judge mostly found in favour of the council.
Since then its staff have talked to Handley.
"The other party and ourselves have settled the outstanding points in contention. They are all resolved," Manning said.
The council's next move is to negotiate sales with the nine landowners involved, who include the Conservation Department and KiwiRail. Manning hopes the council will not need to take land under the Public Works Act.
Then it can call for construction tenders, and building could start this summer.
The council must find a way to provide access, he said. The beach settlement has 85 houses and about 70 permanent residents, rising to a possible 300 in summer. It is on a no-exit road.
The road also services Silver Fern Farms' Waitotara meatworks, which has 350 staff at peak. Most of those commute from the Whanganui area. And the road services the Richard Alexander Quarry, with three to five staff.
The new road will be 8.1km long and have a 6m carriageway. It will carry up to 500 vehicles a day and cost an estimated $5.3 million.
The NZ Transport Agency supports it, and is expected to contribute most of the cost.
The single-lane Limeworks Bridge, built in 1989, has been affected by a series of floods.
When access to Waiinu is cut off Nukumaru farmer David Pearce has allowed people to move across his farm, which has been inconvenient.
"He has been very generous and community spirited throughout this process," Manning said.
The main problem with the bridge is that the Waitotara River is threatening to wash out the banks at either end. In the June 2015 flood one end dropped. The bridge sagged, and was "hauled back into place".
The bending could cause metal fatigue and engineers say it can't last much longer. It carries about 600 vehicles a day, including heavy trucks. When the new road is built, use of the bridge will be restricted to cars.
"If we are able to get trucks off we could make it last longer," Manning said.