Highways England has started procurement for the controversial £1.25bn Stonehenge Tunnel.
Planning permission has not yet been granted for the scheme, which requires an 18-month procurement process, and funding questions are also in the air after the chancellor banned the previously planned PFI model.
However, Highways England is pushing ahead on the basis of development funding it already has received to keep momentum up before the project start date of 2021.
Highways England project director Derek Parody said: 'We expect this scheme to be of interest to some of the world’s best construction companies, who want to be part of delivering this transformational project – a scheme which will not only unlock congestion along this vital A303 route, conserve and enhance the Outstanding Universal Value of the World Heritage Site but also benefit the local and regional economy by providing skills and job opportunities for businesses large and small.
'This in no way pre-empts the outcome of the ongoing Development Consent Order Examination. While this continues to progress, we need to begin the procurement to put us in a position to be able to start construction on schedule in 2021, providing consent is given.
'The start of the procurement process demonstrates the Government’s continued commitment to this scheme and an expectation that progress on it continues as planned.'
The dual carriageway scheme - officially called the A303 Amesbury to Berwick Down - will be eight miles (13 km) long in total with a twin-bore tunnel approximately 2 miles (3,3 km) long through the World Heritage Site (WHS).
As part of wider route improvements there will be a northern bypass of Winterbourne Stoke with a viaduct over the River Till valley and a new junction between the A303 and A360 to the west of and outside the WHS, replacing the existing Longbarrow roundabout.
There will also be a new junction between the A303 and A345 at the existing Countess roundabout.
Plans for the scheme, which have been subject to change following public consultation, are outlined in the contracts work notice published by Highways England in the Official Journal of the European Union.
The OJEU contract notice covers the £1.25bn main works contract for the construction of the tunnel’s civil, structural, mechanical, electrical and technology components, including the tunnel boring machine, along with the approach roadworks and structures and the environmental components of the scheme.
The procurement model is through competitive dialogue allowing a period of design development and dialogue during the tender phase when solutions are developed and tested for compliance with the development consent order requirements prior to awarding a contract.
In total the duration of the 'contract, framework agreement or dynamic purchasing system' could be from 4 January 2021 to 31 of December 2034.
'Highways England is looking to work collaboratively with a high performing partner, their supply chain and stakeholders to successfully realise the aims of this challenging and rewarding scheme,' the notice states.
The appointed contractor will be required to liaise with Highways England, its maintenance contractors and Wiltshire Council to coordinate activities and tunnel operations.
The notice also states: 'There is an extended maintenance period (minimum of 5 years, maximum of 7 years) after construction to 'prove' the tunnel performs as intended. Maintenance is included as part of this period and the contractor will be responsible for all elements of the infrastructure associated with the tunnel and its approaches.'
Contracts for enabling preliminary work will be procured separately, as part of the total £1.7bn capital cost of the scheme.
The scheme is operating on a razor tight value for money calculation, much of which is attributed to heritage benefits, and the Public Accounts Commission, the National Audit Office and the UN have all raised concerns.
The overall project is costed at between £1.5bn and £2.4bn.
For potential contractors interested in more details of the procurement process for the A303 Amesbury to Berwick Down scheme (project reference PQQ_750), go to Highways England’s procurement portal Bravo.