The longest tunnel ever built in Ireland has been completed in Co. Mayo.

The 4.9km tunnel has been under construction since January 2013.

The tunnel runs under Sruwaddacon Bay, a special area of conservation (SAC) and will house a key onshore section of the Corrib gas pipeline. The tunnel will be used to connect the previously laid 83km offshore pipeline from the Corrib Field to the Bellanaboy Bridge Gas Processing Terminal.

Excavation of the Corrib tunnel started in January 2013 using a German designed tunnel boring machine (TBM) called 'Fionnuala'. The 140 metre long TBM and its crew have been working around the clock drilling through rock, sand and clay at depths of between 5.5m and 12m under Sruwaddacon Bay.

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Construction of the tunnel was undertaken by a joint venture between BAM Civil and Wayss & Freytag, both operating companies of Royal BAM Group. As the TBM advanced, over 25,000 concrete ring segments, which were pre-fabricated in Ireland were installed to line the tunnel.

Speaking after the TBM had broken through the final metres of rock at the Glengad landfall site in North Mayo, Michael Crothers, Managing Director of Shell E&P Ireland, said: "On behalf of the Corrib partners Shell, Statoil and Vermilion, we congratulate the entire team on a remarkable achievement. The completion of the Corrib tunnel brings us a step closer to producing First Gas in 2015 and to improving security of supply for the Irish energy market."

Good progress continues to be made on other significant elements of the Corrib project. Approximately 1,000 construction workers are currently employed putting the finishing touches to the project in Mayo, Donegal, Dublin and offshore at the Corrib field.

(CD)