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Client: Direct Route (Limerick) Limited
Contractor: Sisk, Lagan, Roadbridge, Strabag Project
Value: €600 million

Roughan & O’Donovan undertook the design for construction of the non tunnel elements of Limerick Southern Ring Road Phase II PPP project. The scheme provides a dual carriageway which forms part of a ring road linking the Dublin, Cork and Galway inter-urban routes. It consists of approx 9.75km of 2x2 lane dual carriageway and includes a multispan viaduct, 3 creek bridges, 6 road bridges and a 600 meter long causeway. Roughan & O’Donovan designed the bridges/structures, road alignment and earthworks design for the non-tunnel elements and provided resident site staff to supervise the execution of the works.
Innovations & Challenges: The mainline is constructed on low-lying ground with deep alluvium soils adjacent to the Shannon estuary. It is subject to extensive settlements and stability concerns during initial construction. A variety of earthworks solutions were developed to overcome these issues. Use of pre-tensioned concrete W-beams with 44 m span, the longest span used in Ireland to date. Several multi-span, fully integral bridges and viaducts with lengths up to 178 meters. See Paper prepared by Fintan Buggy on Control of Secondary Creep in Soft Alluvium Soil Using Surcharge Loading