The scheme involves the on-line/off-line improvement of the A6 trunk road from single carriageway to dual two-lane carriageway between Dungiven and Drumahoe in Northern Ireland.
Roughan & O’Donovan (ROD) delivered the detailed design for 25.5km of dual carriageway between Dungiven and Drumahoe, and we currently have a full-time designers site team working closely with the design offices and a contracting team monitoring construction of the works.
We developed the detailed design in accordance with the Design Manual for Roads and Bridges and relevant technical memoranda, including Eurocodes and their UK National Annexes, as implemented in Northern Ireland.
Our technical outputs were subject to the rigorous approval procedures of:
- Transport Northern Ireland, the project manager
- Structures Technical Approval (TAA) stakeholders
- DfI Rivers
- Loughs Agency
- the geotechnical advisor
Our structures designs were also subject to Category II and Category III checks.
ROD also delivered the detailed design for the 15km dual carriageway scheme between Castledawson and Randalstown on the A6.
- 25.5km of new dual carriageway (D2AP)
- Four new compact grade separated junctions
- Three new roundabouts
- 22 bridges, including ten overbridges, four underbridges, seven river bridges and an underpass
- 68 culverts, including precast box culverts and arches
- Five retaining walls
- Four environmental barriers
- Five variable message signs
- Over 150 advanced directional signs
- Earthworks design
- Ecological surveys and reporting
- Environmental mitigation works
- Online widening of existing single carriageway
- Health and safety duties
Securing the approval of a diverse range of stakeholders and delivering the detailed design of the structures, earthworks and road alignment to an ambitious timeframe presented key project challenges.
Soft ground to significant depth and environmental issues added further complexity.