A Palmerston North company, RST Environmental Solutions, has brought the revitalised traditional method of preventing erosion using a combination of willow branches and earth to Oamaru.
The only other places in the South Island where it had been used were Southland and Stewart Island, company project manager Jarred Bird said.
It is the company's first contract with the Waitaki District Council.
The method, described as a "bio-engineered, brush-layered retaining wall", could be the answer to stopping erosion of banks on hilly parts of Oamaru, instead of the more costly and less visually appealing concrete or block walls or gabion baskets (wire baskets filled with stones).
Mr Bird said the cost of the brush-layered wall could be up to half other alternatives.
Council roading assets manager Michael Voss said the Avon St contract was worth $100,000.
"A bio-engineering solution was chosen as an alternative to 'grey' engineering (concrete and rock) as it has a similar outcome, is generally cheaper and uses more local materils with less carbon footprint," he said.
Mr Voss was interested in using it wherever possible and appropriate in the Waitaki district, but at this stage did not have other sites selected.
Mr Bird said work started on Monday on the 60m-longwall, which is up to 7m high. The bank was shaped with a digger and yesterday, layers of sterile willow brush and earth were built.
The shrub willow quickly grows, its roots intertwine to lock the bank in place and the tips grow vertically up to 3m high, thin enough to be trimmed with a vertical mower.
The result is a living and stable erosion-resistant bank.
Mr Bird said the way the willow and earth was layered offered protection from the start, and it improved as it grew.
The sterile willow, grown at the company's nursery, and coppice harvested annually, will not spread nor sucker.
Avon St is reduced to one lane during the day while the wall is being built.
The work is expected to be completed about the middle of next week, depending on weather.
A temporary walk and cycleway is available, and access to properties is maintained.
