Limestone bedrock is the most common rock found in Ireland and is formed of the disseminated fragments of shells of calcareous animals that lived on or above the sea floor about 350 million years ago.
Limestone is subject to karst which is solution by rain or groundwater. The most famous example of this is located in the Burren, Co. Clare. Karst landscapes provide many interesting features such as caves, sinking streams and enclosed depressions or sinkholes, known locally in east Waterford as ‘falls of ground’ or ‘breaking ground’. These landforms are a geohazard to construction causing subsidence if not adequately addressed during design and construction.
One limestone type, known as Waulsortian, can be particularly subject to karstification. This rock can be found from Farnanes, heading east through Ballincollig, Cork city and Midleton as far as the coast and from Rathcormack through Tallow and onto Dungarvan. It also crops up (pardon the pun) in other areas such as Cloyne and Youghal (see light blue shading in GSI mapping). The photos of the sinking steam were taken near Cappoquin during ground investigation works for a new domestic dwelling.
Subsidence can occur in many ways such as unidentified sinkholes or punching failure of driven piles. It is also a geohazard for our poor probing rods where we slide along a pinnacle during probing until refusal is met at the base. If you live in any of these areas, contact Substruck for a professional approach to ground investigation.