Mr. Koen Verbruggen:

There are some slides relating to groundwater, as it is an area of concern. The Geological Survey of Ireland, as part of the larger Department, provides technical and independent geological advice, including in the groundwater area, where we also work with the EPA. The circulated document demonstrates the importance of groundwater as a drinking water resource, and it can constitute up to 80% of the water supply in some counties. Some 68% of group water schemes serving 20 or more people are supplied by groundwater boreholes or springs and we are aware that there are up to 200,000 private wells in rural areas not served by public or group water schemes, and where groundwater is usually the only source of supply. We have a detailed map showing the level of information we have across all the country, and we can take the north west as an example. Groundwater resources or aquifers where there is a water supply can be categorised based on its importance and strategic value. Most of the rural houses and farms would have their own bore and spring, and not all boreholes are necessarily known or mapped. From the data we have, the deepest water supplies known in the area are approximately 140 metres.

As part of risk assessment we produce a groundwater protection or vulnerability map, showing the areas where groundwater is most at risk from surface contamination. By combining the importance of the aquifer with the thickness of cover and nature of geology, we can produce planning maps used by the local authorities and in development plans. With regard to contamination pathways, the highest threat is considered to be contamination from boreholes, and engineering solutions are considered to ensure that does not happen. Gas leakage from below the aquifer along fractures is also an issue, and it should be pointed out that from what we know of the geology, existing faults are relatively tight in the area. Seismics or acoustics are used to monitor and model the process. Gas exploration within or adjacent to the aquifer which could cause lateral migration would seem to be unlikely due to lack of permeability or large lateral distances. It is nonetheless considered a potential source of contamination.