Dunkettle Interchange


Location: Cork, Ireland
Client: John Sisk & Son Ltd.
Status: Ongoing
Overall Project Value: €100m

Brief Description

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.
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FT Responsibilities

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

Project Statistics

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12 major structures of various forms are being developed

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4 roundabouts are being developed

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9 culverts are being designed where the scheme crosses watercourses of intertidal areas