Finian McGrath (Dublin North Central, Independent)
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Question 334: To ask the Minister for Transport the reason for tens of thousands of litres of water continuing to leak unabated into the Dublin Port tunnel each day for the past eight weeks and more, and the tunnel engineers and Dublin City Council saying that this water is groundwater, despite the fact that there has been little or no rainfall in the past two months; if aquifers (details supplied) are draining into the tunnels, the measures which are being taken to fill or stabilise the voids they are leaving and to prevent further subsidence being caused beneath the houses in Marino; and if he will make a statement on the matter. [8103/06]

Martin Cullen (Waterford, Fianna Fail)
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The planning, design and implementation of national road improvement projects, including the Dublin Port tunnel, is a matter for the National Roads Authority, NRA, and the local authorities concerned, in this case, Dublin City Council.

I understand from the NRA that dealing with water infiltration during the construction phase is part and parcel of the process of building any tunnel that passes below the surrounding ground water level. It is routinely encountered and dealt with on tunnel projects throughout the world and is being similarly dealt with in the Dublin Port tunnel. I am informed that any measures necessary to deal with such groundwater issues will be implemented by the contractors at their own expense.

The Dublin Port tunnel passes up to 20 m below the ground water table along the route. At this depth the issue of rainfall over the previous two months has no significance. I understand that the water infiltration is simply groundwater contained within the rock surrounding the tunnel and that no voids can, or could, result from such water movement. I am also informed that there is no possible issue of subsidence associated with such water infiltration.

Construction work on the Dublin Port tunnel has been monitored in detail since the project commenced in 2001 by construction supervisors appointed by Dublin City Council. When problems arise, as they inevitably and routinely do with projects of this size, Dublin City Council and its construction supervisors ensure that they are detected and rectified. Contrary to the impression that may have been created, there are no safety implications, either for the workers on the tunnel, for the structural integrity of the project or for the buildings and houses above the tunnel.