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A road resealing crew at work in the Waipoua Forest on SH12

Kauri dieback precautions adopted for SH12 resealing works

Waka Kotahi NZ Transport Agency has been working hard to help protect the precious Waipoua Forest from kauri dieback disease, committing to using special preventative measures for workers and equipment.


The Transport Agency’s contractors have repaired and resealed 11 km of State Highway 12 through the Waipoua Forest in Northland – part of the Twin Coast Discovery Route – and adopted special practices to protect against the spread of the disease.

The kauri dieback disease is devastating kauri trees in the Waipoua Forest, which is home to New Zealand’s largest known living kauri tree, Tane Mahuta. The disease is easily spread through soil being carried on dirty footwear or by animals, equipment and vehicles.

Transport Agency Northland system manager Jacqui Hori-Hoult says it was the first time there had been major work on the road since it was completed in 1996. Contractors had to dig up the road surface to carry out repairs before resealing, as well as rebuilding the roadside drainage system and cutting back vegetation.

“To drive the winding state highway through the forest is like taking a journey back in time to before European settlement and logging transformed the landscape. The forest grows right up to the road’s edge, with the tree canopy overhanging the road. It’s home to many rare native plants, including native orchids. It’s a pristine and spectacular environment and we wanted to do everything we could to preserve it,” Ms Hori-Hoult says.

“Because of kauri dieback, the road team had to clean all vehicles and equipment before going into the forest and when they came out. Everything they disturbed – whether they were digging up the road surface, trimming vegetation or fixing the roadside drainage – had to be picked up and taken out of the forest to a contaminated waste dump.”

No known cure

It’s the first time since the discovery of kauri dieback that a roading project of this scale has been undertaken. A disease caused by a microscopic fungus-like organism called phytophthora agathidicida (PA), kauri dieback is killing trees of all ages. It lives in the soil and infects kauri roots, damaging the tissues that carry nutrients and water within the tree, effectively starving it to death. There is no known cure.

Waipoua is a former state forest, now managed by local iwi Te Roroa with governance support from the Department of Conservation, Ministry for Primary Industries, the Northland Regional Council and local councils, the Transport Agency and roading contractor Fulton Hogan. The work was carried out under the Waipoua Forest Management Plan which covers the edge of the road and its interface with the forest. The plan manages the effects of the highway on the forest’s biodiversity.

Te Roroa development group general manager Snow Tane says it was a good team effort. “Te Roroa is thankful for the commitment and support from Waka Kotahi and roading contractor Fulton Hogan to the work undertaken in Waipoua, including their response to mitigating against kauri dieback which is essential to the wellbeing of the ngahere (forest).”

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