M25 J12-15 Widening and T5 Spur Stage 2

In December 2005, widening of the M25 motorway close to Heathrow Airport was completed, together with the new M25 spur road which now serves Heathrow Terminal 5. This 12km stretch of motorway is the busiest in Europe, with up to 200,000 vehicles passing through the site every day. The existing dual four lane motorway was widened to dual five lanes between junctions 12 and 14, and dual six lanes between junctions 14 and 15, all within the existing highway boundary. 

The scheme was highlighted as an exemplary delivery during the keynote Best Practice presentation at The Highways Agency Major Projects Conference 2005.

Gifford, as part of the Gifford WSP Joint Venture, was employed by Balfour Beatty to implement the design of the motorway widening and new Terminal 5 spur road as part of a Design and Build contract.  

• All widening needed to be within the original highway boundary, with four lanes remaining open except during limited overnight closures
• The total contract period was 137 weeks, with 102 weeks on site for construction. The project was opened three weeks early
• Rapid construction was facilitated by the modular system design adopted for the retaining walls used for widening the existing motorway.

• Concept design at tender stage
• Design of five new steel composite bridges, including a three span bridge carrying the spur road over the existing motorway, and a landmark structure over the River Colne
• Highways design, including alignment, drainage, safety fencing, junctions and biological ponds
• Geotechnical design, including earthworks widening, reinforced earth slopes, soil nailing, stone columns and pile design
• Design of 4.8km of new retaining wall
• Design of 40 new gantries, utilising standard Gifford gantry system designs
• Design of modifications to over ten other existing structures of significance, including widening to two railway under bridges and pier strengthening to four over bridges
• Detailed design developed to facilitate contractor’s traffic management proposals