The concrete bridge over Diddah Diddah Creek on Boorhaman East Road, south-west of Rutherglen, will be strengthened after a probe uncovered problems with load capacity.

Indigo Shire Council said an investigation found long-term issues with bridge beams and culverts.

"To accommodate current and future traffic loads within acceptable safety factors, our structural engineers have developed designs to strengthen the bridge and upgrade the culverts," the council said.

"Works will involve the temporary removal of the bridge deck structure to allow the installation of extra supports under the middle of the bridge beams, before they are returned and further strengthened with the addition of a concrete overlay.

"We will also replace and increase the capacity of the culverts on the northern side of the bridge and upgrade the road approaches and safety barriers to accommodate the slightly higher deck level."

The council said if nothing was done, the bridge load limit would need to be "significantly reduced".

The project is jointly funded by a federal Bridges Renewal Program grant and through the council's capital work bridge renewal fund.

The federal government has contributed $483,314, with council putting in $120,829.

The council said designs and tender documents would be finalised over the next two months, followed by a tender process to select a contractor with works "hopefully able to commence in the spring".

"As the project develops, we will work with the community and businesses to minimise the impact of these works, but it is likely the bridge will need to be temporarily closed to permit works to progress safely and efficiently," the council said.

"Detours will be in place to redirect traffic during this time."