Subsoil is the layer of soil under the topsoil and on top of the bedrock. The ease with which water can pass through the subsoil is known as the ‘permeability’.

The subsoil permeability affects how easily rainwater can soak down into the ground and fill up the groundwater resource (aquifer). An aquifer is a body of rock and/or sediment that holds groundwater.

The Subsoil Permeability map shows how permeable the subsoils are in Ireland. The map shows the subsoil permeability category at any point on the land surface as long as the subsoil is greater than 3 metres thick. There are three categories: ‘High’, ‘Moderate’ or ‘Low’.

Geologists map and record information on the subsoils above the bedrock. They find out how deep the subsoil is and how permeable it is. They use information from quarries, deep pits and from boreholes (a deep narrow round hole drilled in the ground).

This map is to the scale 1:40,000. This means it should be viewed at that scale. When printed at that scale 1cm on the map relates to a distance of 400m.

It is a vector dataset. Vector data portray the world using points, lines, and polygons (areas).

The Subsoil Permeability data are shown as polygons. Each polygon holds information on the Subsoil Permeability Code and the Subsoil Permeability Description.