The river is located in the Slieve Blooms which is a special area of conservation.
Laois County Council has to get planning permission from Ireland's national planning body before it can fix a bridge in the Slieve Bloom mountains.
So county councillors were told after Cllr Seamus McDonald, Fianna Fáil, asked the local authority for an update on the bridge at Rearyvalley in a recent meeting with officials.
Cllr McDonald said there had been problems with the bridge for up to quarter of a century but the situation has worsened.
"There was more damage done recently due to heavy flooding," he said.
Cllr McDonald said he feared it would fall in on itself, something that would cause a lot of problems for a local farmer.
"If that bridge collapses the farmer living on the other side will be isolated," he said.
In reply Mr Edmond Kenny, District Engineer, said a national application has to be made.
"Repairs to the structure and river channel are proposed. Due to the extent of the works proposed and the sensitivities of the river an application to An Bord Pleanála will be required. It is anticipated that an application to the Bord will be lodged in 2023," he said.
An Bord Pleanála says local authorities are required to make an application to An Bord Pleanála for any proposed development in their functional area, or on the foreshore, where an appropriate assessment under the Habitats Directive is required.
The issue was raised at the December meeting of the Borris-in-Ossory Mountmellick Municipal District in County Hall Portlaoise.
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