The Port of Dublin has said a section of the Bay Bridge Tunnel that had been plugged with cement had been repaired and now could be plugged again.

The Port said yesterday that it had been fitted with a “plugs & tunnels” system, which allows for the use of an internal pipe to access a portion of the tunnel to plug it.

The system is a significant step towards fixing a major problem, as well as a major setback for the port, which has been under pressure to make changes to improve the port’s operations and the environment.

It comes as the Irish Times revealed yesterday that the Port was planning to build a tunnel beneath the Bay in the south of the country, and had been granted permission to proceed with a tunnel under the waterway.

The port said it was now considering a plugging of the whole tunnel, which would have a “significant environmental impact”.

The port has been struggling to find funding for the project since last year, when a number of problems arose in the tunnel.

It said last month that it was seeking to raise €500 million from investors.

Last week, it announced that it would invest €200 million of its own money into the project, with the remainder coming from the European Union.

The money would be used to make the tunnel “more attractive to investors”.

It said that in addition to improving the port as a tourist attraction, the project would also help to improve its image as a transport hub, and improve the “environmental footprint”.

The plan for the Bay Tunnel, which was approved in 2011, had been a major priority for the Irish Government, as it was the only major transport tunnel at the Port of Cork.