The 10m (32ft) deep, 16m (53ft) in circumference hole was discovered in a field owned by farmer Eddie Cavanagh on Saturday morning in Co Kilkenny.
It’s directly above a mine shaft which was part of the Galmoy Mine operation, closed recently near Crosspatrick, close to the Kilkenny/Laois border.
Mr Cavanagh saw the hole when he looked out his kitchen window on Saturday and realised its extent when he went outside to examine it.
“What frightened us,” his wife Mary Hilda Cavanagh said, “was that two days before, on the Thursday evening, Eddie and [their son] Brian had been spreading soiled water there. They drove over it”.
The field is normally used for grazing and for cutting silage but is left unused between October and March.
“I wouldn’t be in a hurry into the field again,” Ms Cavanagh, a Fine Gael councillor, said.
Her husband notified the mining company and the 22-acre field was immediately secured by Lundin Mining — owners of Galmoy — who also informed Kilkenny County Council, the Department of Energy and Natural Resources and the Environmental Protection Agency (EPA).
The council also blocked the road, about 200m away, as a precaution.
“It’s quite sheer and quite dramatic,” Kilkenny city and county manager Joe Crockett, who visited the site on Saturday, said. “It’s well set back from the road and is behind the main mining complex at Galmoy.
“The field was cordoned off and security personnel were put on the site by the company, just to protect public safety.”
Initial assessments by Lundin Mining and the Department of Energy and Natural Resources indicate “there are not public safety issues arising”, Mr Crockett said. There was no need to evacuate any nearby homes or buildings.
A meeting between company officials and the various state agencies with an interest in the issue was held yesterday morning and geological and hydrogeological assessments will continue over the coming days.
There has been speculation that the amount of rain experienced in recent weeks may have weakened the earth above the mine shaft but, according to Joe Crockett, no reason for the opening of the sink hole has yet been confirmed.
“It’s as if the surface just dropped away. Until the assessments are complete it will be impossible to give a reason.”
There was initial concern at the weekend, he said, about the possibility of more such sink holes developing, but experts now agree that “there aren’t public safety issues”.
Lundin Mining’s vice- president for technical services, Steve Gatley, has been on site and confirmed that the sinkhole was overlying part of the former underground workings of the closed mine.
“In co-operation with the landowner we have cordoned off the surrounding area and we are working closely with the relevant statutory authorities to agree next steps,” Mr Gatley said in a statement. “We will also be investigating the matter fully over the coming days with independent hydrogeological and geotechnical support.”