Watch your step down west!
A large sinkhole, more specifically known as a ‘crown hole’, occurred this week on a public road in West Cork.
It is believed that mines dug during the once prominent local copper industry, dating back to the 19th century, may have been the cause for the collapse. The incident occurred at Kealogue, near Allihies on the road to the Beara Peninsula, just yards from a residential property.
The Cork Independent spoke with a representative of Geological Survey Ireland (GSI), the national geoscience data centre.
Speaking about the incident, the representative said: “It is important to note that the event that has occurred in Allihies is not a ‘sinkhole’ but rather a ‘crown hole’. Some form as a result of the collapse of old, shallow mine workings, often triggered by heavy rainfall events. The ground collapse at Kealogue (Allihies) is inferred to be a collapse of ground coincident with a known 19th century shaft.”
GSI undertakes geological mapping for government agencies, including matters relating to the subsurface, such as old mine sites.
The crown hole became apparent over the weekend before collapsing, leaving a deep hole in the road. According to GSI, similar events are a frequent occurrence in Ireland. GSI’s data has recorded up to 9,000 karst sinkholes and crown holes in Ireland, generally occurring in limestone areas.
“In the vicinity of the ground collapse, the mine workings extend to depths of over 400m. However, the collapse at Kealogue is most likely related to the failure of near surface workings,” continued the representative.
Following the collapse, Cork County Council released a statement saying: “Cork County Council wishes to advise that a large deep sinkhole has developed to the south of Allihies village on the Beara Peninsula. It appears that the sinkhole is linked to the collapse of a mine shaft in Cahermeeleboe, Allihies. Cork County Council urges vigilance and advises that caution should be exercised by all in this area.”
Crown holes typically occur as the result of historic mining whereas modern mining takes preventative measures to avoid such incidents.
“Modern mines design their extraction to mitigate subsidence. In addition, a Closure, Restoration and Aftercare Management Plan is put in place which typically incorporates subsidence monitoring. Most modern metal mines backfill the mined voids,” said GSI.
The road was closed as a result of the collapse which could potentially enlarge further. Barriers are currently in place to prevent access.
Following a collapse, crown holes are often filled. However depending on the depth, it may have to be cordoned off. It represents a substantial safety risk. However no accidents occurred and the road remains closed. GSI stated that injuries as a result of such incidents are “extremely rare”. Members of the public are being asked to avoid the area and to stay behind the safety barriers in place.