Dublin City Council has stated that there is no reason for alarm after it was revealed that water was leaking into Dublin Port Tunnel at the rate of half a litre a second.

The leak is the third identified in 18 months. It is located on a crossover point between the two tunnels at an area below Marino Park in north Dublin.

The Council claims that the section of the tunnel crossover should have had walls of pumped concrete 400mm (15.7ins) thick. It seems though, that hollows developed in the concrete where it was being pumped. This led to a thickness of just 300mm in some parts.

Water from fissures in the rock face built up behind the wall and was seen as a problem over a four square metre section.

Although the Council said the issue was routine, the senior engineer in charge of the project, Tim Brick, said he would have preferred if the contractor "had been right initially".

He stated that the project was "still on target" but that the tunnel would open by next May when it would provide an eight-minute link between the Dublin port and the M50.

Repair work will be carried out over the next two weeks by contractors working for the main contractor, the Nishimatsu Mowlem Irishenco consortium.