The damage was identified after an inspection was conducted following last winter’s flooding.
The planned underwater repair works, funded by the Department of the Environment, will commence in the coming weeks. A €150,000 contract was awarded to Irish Sea Contractors based in Rosslare.
The city council said that traffic disruption during the repair works will be minimal.
Pat Eyres, senior executive engineer with the city council, said: “Last winter, the Shannon was at its highest levels ever recorded — with up to 800 tonnes of water per second coming down the river, plus the tide going out through the bridge.
“Water, when it gets going, can scour and carry material much bigger than normal with it.
“Following the deluge, we inspected the bridge and discovered the situation was not critical and there was nothing to be worried about.”
However, if the bridge has to be closed off during the repair operation, the city council can avail of a number of traffic flow options.
Traffic through the city centre could also be diverted over Shannon and Thomond Bridges.
But, most likely, it will not be necessary to close off the bridge completely for repairs.