Tumby Bay District Council is excited with the developmental and environmental benefits of an upgraded Graham Smelt Causeway culvert, with work expected to start early next year.
The state government has committed $1.6 million from its Local Government Infrastructure Partnership Program to the project with council to match this funding.
Works are expected to begin in January next year and will see the current culvert, built in the 1980s, replaced with one built to a higher specification with a 100 year useful life.
Tumby Bay mayor Sam Telfer said this project would further assist with the town's capacity for growth.
"We are working hard to invest in new and upgraded infrastructure that will support the residential growth we anticipate to see as significant industrial projects come online," he said.
As well as helping with the the town's residential growth the project is also expected to reinstate a more natural tidal flow into the town's mangrove wetlands.
Department of Environment and Water Director Climate Change, Coast and Marine Dr Neil McFarlane said improving the tidal flows would help improve the condition of what is a nationally-listed temperate saltmarsh ecosystem inland of the culvert.
"Coastal saltmarsh and mangrove ecosystems provide breeding grounds for fish, a buffer to protect inland areas from coastal storm damage and are important for capturing and storing carbon", he said.