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Brynglas Tunnels Refurbishment

Client Costain
Project Value £34 million
Status Complete

The multi-disciplinary Capita Infrastructure team was appointed in 2015 by Costain on the detailed design of the highways, structural repairs to the Malpas Viaduct and Brynglas Tunnel refurbishment and co-ordinated their works to accommodate the Client designed post tension strengthening of the Usk Bridge.

The Brynglas Tunnel is situated on the M4 Motorway under Brynglas Hill in Newport, South Wales. The 370m twin-bored tunnels were the first tunnels in the British motorway network and are still the only bored tunnels. The project was commissioned to enable the continued delivery of effective transport links and resilience of the network by protecting the Tunnels, River Usk Bridge, and Malpas Viaduct (and therefore the M4 route) from further deterioration. It reduces the vulnerability of the structures and the risk to life safety during major incidents, particularly those involving fire.


Prerequisites for the project included:

  • To design and deliver an innovative technology solution to improve the efficiency of the Tunnel;
  • Replace the existing pavement and drainage system in its entirety over 8, part weekend closures;
  • Deliver the works to a stringent closure programme;
  • Maintain existing assets whilst new innovative solutions delivered;
  • Undertake works with the minimum disruption to road users and stakeholders.


In September 2018, the project also secured a ‘Very Good Whole Team Performance’ CEEQUAL rating. In December 2018, the project was Highly Commended in the ‘Innovation in Design & Delivery’ award at the NCE Tunnelling Festival 2018, specifically in relation to the pavement and drainage design. The project has been awarded a further two Constructing Excellence in Wales Awards and ICE Award. These include the prestigious 2019 ‘Civils Project of the Year’, a highly-commended award for the ‘Innovation’ category, and the ICE “Chairs Special Project Award”. This complex scheme was delivered on time and on budget by a collaborative Capita, Costain, and Arcadis team for the Welsh Government.




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