John Sisk & Sons Holdings Ltd (Sisk). have been commissioned by Transport Infrastructure Ireland (TII) to develop proposals for the improvement of the existing Dunkettle Interchange.
The Scheme comprises:
- A series of direct road links between the N8, the N25 and the N40 and links to the R623 Regional Road in Little Island and Burys Bridge in Dunkettle.
- 1 grade separated junction arrangement at the existing N25 to the east of the existing Dunkettle Interchange.
- 4 roundabouts – 2 at grade separated junctions and 2 at grade tie ins with the existing road network.
- 12 major structures of various forms.
- 24 gantries
- 9 culverts where the scheme crosses watercourses of intertidal areas.
- Intelligent Transport Systems.
- Pedestrian and cyclist facilities.
In addition, the works include the modification of the existing Silversprings junction on the N8 Lower Glanmire Road comprising:
- Construction of a new raised central reserve on the N8 Lower Glanmire Road.
- Reconfiguration of the N8 westbound diverge.
- Reconfiguration of the N8 eastbound merge and diverge.
- Pedestrian and cycling facilities.
Sisk appointed FT, Ramboll UK and Clandillon Civil Consulting (FTRC) to carry out the design for the scheme. FT is the Lead Consultant and a partner in the geotechnical team with Ramboll UK. FT Geotechnical team provided key elements of the geotechnical scope of works including:
- Jointly scoping the Site Investigation and producing specification documents
- On site supervision of site investigation contractor – including trial pitting, cable percussion, rotary boreholes, geophysical investigation and geo-environmental assessment
- Groundwater monitoring
- Joint interpretation of ground investigation data and production of a Ground Investigation Report
- Liaison with external experts for peer review of design
- Earthworks design using a variety of ground treatments, including controlled modulus columns, band drains, excavate and replace and surcharging including structural transition zones
- Foundation design for all structures on the scheme (bridges, retaining walls and gantries), including pile design on soft ground
12 major structures of various forms are being developed
4 roundabouts are being developed
9 culverts are being designed where the scheme crosses watercourses of intertidal areas