Trunk road tunnel benefits environment and cuts journey times

The A3 trunk road is a major highway between London and Portsmouth on England’s south coast. To tackle congestion and improve safety on this busy route – which carries an average of 28,400 vehicles per day – the Highways Agency is implementing a 6.5km dual two-lane highway scheme at Hindhead in Surrey. The scheme includes a 1.8km twin-bore tunnel which removes the trunk road from Hindhead village and from the Devil’s Punchbowl, a famous natural landmark designated a Site of Special Scientific Interest and part of a Special Protection Area.

Mott MacDonald is designer to Balfour Beatty, contractor for the £371 million project which is being delivered using the Highways Agency’s innovative Early Contractor Involvement (ECI) approach to design and build – devised to speed delivery and enhance value for money by involving the contractor from the project outset. As part of an integrated single team with the Highways Agency and their consultant for the Hindhead project, we are responsible for all design aspects of the twin-bore tunnel and the highway, including civil, structural, geotechnical, mechanical, electrical, fire and safety systems engineering. Specialist assistance is being provided by Wessex Archaeology, landscape and ecology consultant RPS, and statutory procedures advisor Persona Associates.

The Hindhead tunnel will be the longest non-estuarial tunnel in the UK. It will feature cross-passages every 100m and state-of–the-art safety and communications systems, including high quality lighting and ventilation, CCTV surveillance and radio-interrupt systems to convey quick appropriate information to tunnel users. The ground conditions are predominantly sandstone and the tunnel bores will be constructed using sprayed concrete lining. The target completion date is 2011.