Residents install warning signs along Corrib tunnel route

CONCERNS about sinkholes along the tunnelling route for the last section of the Corrib gas pipeline at Sruwaddacon Estuary have led residents to instal warning signs. They say they were forced to erect the signs, which state ‘Danger Sinkholes: Keep Back’, because neither Mayo County Council nor the Department of Energy and Natural Resources had taken action.
The residents claim the sinkholes began to appear on May 20 and can be up to eight-foot in depth.
However, a spokeswoman for Shell said they are not sinkholes but rather ‘small localised depressions’ caused because of ‘the permeability of the ground above the TBM [Tunnel Boring Machine]’.
“Small air losses have happened at times during interventions since tunnelling started, but have posed no risk to public safety. We inform relevant authorities of these occurrences as appropriate,” she said in a statement.
The spokeswoman explained that these small depressions were just one- to two-feet deep and filled naturally with the ebb and flow of the tide.
“To aid the tidal process, project staff have raked the depressions, on occasions, during low tide. This is in accordance with procedures agreed with the regulatory authorities,” she continued.
The Department of Energy confirmed to The Irish Times last week that it has been investigating reports of ‘sinkholes’ or ‘depressions’ on a north Mayo tidal estuary where the final section of the Corrib gas pipeline is being laid.
Speaking on behalf of Shell to Sea, Terence Conway said that Shell has deployed up to ten workers with shovels to fill in these sinkholes but they had failed.
“We can currently follow the path of the tunnel by the trail of sinkholes that  have appeared on the strand,” Mr Conway said.
The area where the indentations have been seen lies above the route where the 500 tonne TBM – named Fionnuala by Shell after one of the Children of Lir – has been deployed to dig a 4.9km sub-sea tunnel.