Image courtesy of Sacyr, Wills Bros Ltd, Somague.
Summary
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.
Solution
Roughan & O’Donovan delivered the detailed design for 25.5km of dual carriageway between Dungiven and Drumahoe and provided a full-time designers site team, who worked closely with the design offices and the construction 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.
The scheme officially opened to traffic on Friday, 7 April 2023.
ROD also delivered the detailed design for the 15km dual carriageway scheme between Randalstown and Castledawson on the A6.
Design elements
- 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
Challenges
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.
Services provided:
- Tender design
- Value engineering
- Project management
- Geotechnical Advisor role
- Flood risk assessment
- Watermain and foul sewer diversions and new works design
- Scoping advanced data gathering contracts including topographical, geotechnical, structural, CCTV
- Scheme detailed design – all disciplines including 22 bridges, with 6 major river crossings with spans up to 80m, ITS, VMS gantries, over 90 culverts, retaining walls and boundary walls
- Securing technical approvals
- Ecological surveys and reporting
- Environmental mitigation and implementation
- Full time designers site team with responsibility for monitoring, progress reporting and supervising the works
- Production of as built records, structures maintenance manuals, roadworks maintenance manual and geotechnical feedback report
- Contribution to CEEQUAL submission
