Limerick Tunnel

Limerick Tunnel Public Private Partnership (PPP) Scheme

Our client
Van Oord Ireland Ltd are sub-contracted to Directroute (Limerick) Construction Limited, for the undertaking of the marine elements of the works for the Limerick Immersed Tube Tunnel.

Directroute (Limerick) Construction Limited is a consortium comprising Strabag AG, John Sisk & Son (Holdings) Limited, Lagan Holdings Limited, Roadbridge Limited. Directroute were awarded the main contract by the National Road Authority, Ireland.

Our work
The project involves the crossing of the River Shannon by means of an immersed tube tunnel. Van Oord's element of the works includes dredging a 400 m long, 16 m deep trench across the River Shannon between the extremities of the cofferdam/float-out structures. The dredged material was pumped into sedimentation lagoons; the design of which ensured that the turbidity of the return water fell within strict environmental limits. 

Completion of the trench was followed by the flotation, transportation and immersion of five reinforced concrete tunnel elements, each measuring 100 m long, 20 m wide and 8 m high and weighing 18,000 tonnes. These were positioned on temporary large concrete tiles on a gravel bed, before being finally supported on a foundation formed by sand-flowing underneath the tunnel floor.

The tunnel is backfilled and surrounded by 75,000 tons of rock and approximately 250,000 m³ of the original ground material.

The operations took place on a shallow tidal river with strong currents and a 6 m tide difference.

Our result
Once completed, the main contract, which involves the construction of 10 km of new dual carriageway will relieve the third largest city in Ireland from traffic congestion at both sides of the city bridges across the river.