Work will begin at Mullumbimby's Lavertys Gap weir in September to repair serious erosion along the creek bank.
Erosion has been progressing for some time and was worsened during the 2022 floods and Cyclone Alfred earlier this year.
Byron Shire Council Manager Utilities Cameron Clark said the work at the 100-year-old weir on Wilsons Creek will protect and preserve one of the Shire's most important heritage assets.
"The weir is the main source of drinking water for Mullumbimby and is listed on the NSW State Heritage Register," Mr Clark said.
"Without repairs there is a risk of channels forming in the earth around the weir wall, causing leaking.
"NSW Public Works will carry out repairs that will preserve the heritage fabric of Lavertys Gap weir and secure its long-term integrity."
Water cannot be drawn from the weir during the repairs and Mullumbimby will be temporarily supplied with water from the recently extended Emergency Water Main.
The Mullumbimby Emergency Water Main was upgraded in 2025 to support all of Mullumbimby, whereas previously it could only supply about half the town.
The main is connected to the Rous regional water network, which supplies the rest of Byron Shire.
There will be no disruption to supply and residents will not experience any changes to their water service during the works.
The project is expected to take approximately 16 weeks. Flows in Wilsons Creek will be maintained by pumping water past the weir wall.
Information about the repair of Laverty's Gap weir is on Council's website.
The work is being carried out under the NSW Government Water and Wastewater Repair and Recovery Program.
