The pedestrian track constructed from native timbers has been registered as a category 1 historic place and work is under way to reinstall it.
Dunedin City Council property services general manager David Bainbridge-Zafar said the installation design had been completed and it included a display unit where temperature and humidity would be controlled to ensure the causeway’s continued preservation.
The council had been working closely with Heritage New Zealand Pouhere Taonga on the project to display part of the causeway in the mall and the council was delighted to see it listed as a category 1 heritage item, he said.
The registration process did not affect the timing of the broader project, Mr Bainbridge-Zafar said.
The structure was found in 2008, after demolition of the former Deka building in George St, before construction of the Wall Street Mall.
It was a 12m-long and 4m-wide corduroy causeway, constructed between 1848 and 1859 to bridge an area of boggy ground.
Corduroy is a reference to the ribbed surface of the walkway.
About 40% of the timber was cleaned and lifted out for preservation.
An image supplied to the Otago Daily Times showed how the timber path would be preserved in a display case beneath
shoppers’ feet.
The city council agreed to what has become an estimated $400,000 project after Heritage New Zealand brought a prosecution against it for failing to comply with an archaeological authority.
Contractors had breached work conditions by digging a trench through 19th-century layers of the site.
Southern Archaeology Ltd director Dr Peter Petchey, who has since led excavation and recording work for the council and mall owners, said each piece of timber would be placed at its original location.
He was pleased the causeway had received category 1 status.
"It’s the oldest known structure from those really early days of Dunedin settlement," Dr Petchey said.
Information from Heritage NZ’s listing states the causeway was built from a variety of timbers cut from the local bush, including kanuka.
The timber was cut with axes and no nails or other fastenings were used.
The preserved section, about 40% of the structure, was bathed in chemicals, before drying gradually.
City council heritage adviser Dr Andrea Farminer has said the display would have the appearance of being wet and boggy.
The causeway is the earliest known example of a substantial corduroy road in New Zealand and is considered to have outstanding archaeological significance at a national level.
