Transport for NSW said repair works on the Oxley Highway to pre-flood condition are expected to continue into mid-2023 after more than one metre of rain fell at Mt Seaview, closing the road between Yarras and Gingers Creek in March.

The heavy rain caused significant damage to a 33km stretch of highway, with around 70 landslips occurring, 10 of which are major. More than 22km of the road has remained closed to traffic.

Full access along the Oxley Highway, south-west of Kempsey, was restored between Yarras and Mt Seaview in May, with one small section still single lane.

The main areas of damage are in the mountainous stretch between Long View and Ralfes Creek. At least five of the slips have caused major damage below the highway, and these will be the most challenging to repair.

One of those slips saw 4000 tonnes of soil fall down the mountain.

"This is an enormous job for us to be working on," Transport for NSW regional director Anna Zycki said.

"This large storm event has certainly been one of the biggest we've ever seen in the northern region of NSW."

Ms Zycki said the Oxley Highway was built decades ago and not to the standards a road would be completed if built today.

"Certainly one of our most important considerations is keeping our workers safe while we are doing this work. We need to make sure we are doing it steadily and test the sites as we go to ensure other landslips can't occur while we are doing work," she said.

Walcha mayor Eric Noakes said the road closures have had a significant impact on his community off the back of bushfires and drought.

"It's been a massive impact for us. But when you see what has got to be done, it's a massive job," Cr Noakes said.

Minister for Regional Transport and Roads, Paul Toole, said work was progressing well.

"Restoring access has been a monumental task after the damage we saw - our teams have used every tool and technique at their disposal to get the job done," he said.

Member for Oxley, Melinda Pavey, said opening the road as soon as possible was a priority.

"I know how important the highway is for our communities, local industries and the economy," Mrs Pavey said.

"Crews have been using several techniques to ensure motorists will soon be able to travel along the whole length of the highway, including deploying drones to examine and evaluate damage from a safe distance."

Member for Tamworth, Kevin Anderson, said up to 30 workers had been on site each day, working to remove rock and debris.

"The damage to the Oxley Highway has been immense and has required a coordinated response from Transport for NSW, Walcha Council, geotechnical experts and local contractors," Mr Anderson said.

"Local communities are to be congratulated for their patience and support during this difficult time, and I'm sure they join me in thanking the dozens of workers on the ground who have been working every single day to restore this vital transport link."

Transport for NSW reopened the 12-kilometre section of highway between Yarras and Mt Seaview in May and is working to reopen the section from Mount Seaview Rd to Gingers Creek to single lane in July.

This work includes stabilising the ground under the road at the two largest slip sites. This will be done using a technique called 'soil nailing'.

This technique involves pinning the soil and vegetation onto rock with long steel nails, steel mesh and a concrete facing.

The work currently being carried out is to prevent further deterioration of the road and to provide enough strength to allow traffic through. However, there are several sections where part of the road formation has been lost, and restoration of the road to the original width will require further investigation and design.

This full restoration work to reopen the road to pre flood conditions will take about two years to complete.

Concurrently with the temporary repair work, Transport for NSW carrying out investigations and engineering trials to determine the best way to stabilise the sections that have slipped.

More investigation work will need to be carried out with extensive drilling and soil nailing operations to determine the repair design to allow the road to reopen to two way traffic.

To repair the road to pre-flood condition by May 2023, the road will need to be closed at various times to carry out the works.

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