HS2 has today (Thursday 14 December) released new images showing the Edgcote Viaduct, which it is building to a new, more eco-friendly, design.

The high-speed rail project has changed the structural design of the viaduct, reducing its carbon footprint by more than thirteen per cent. To achieve the carbon saving, engineers followed the approach that was developed for the Thame Valley Viaduct, near Aylesbury. It uses a lightweight, modular design, which reduces the amount of concrete and steel needed.

The viaduct will be manufactured off site at a facility in Kent. The previous design would have seen engineers use five beams for each span, securing them with concrete poured in situ. Instead, engineers will now use two larger, U-shaped beams per span, which they will secure directly to the next pair of beams. The change does not significantly alter the height or length of the viaduct, but will cut the volume of lorry movement and will speed up construction.

The piers will also be narrower and will extend to almost connect with the parapet edge. This will enhance the appearance of a light and narrow structure.

The viaduct will be 515 metres long, between six and eight metres high, and will be supported by twenty pairs of pre-cast concrete piers. It will be set low into the west Northamptonshire landscape, and from a distance, will be largely hidden by existing hedgerows and woodland. It will carry HS2 across the River Cherwell’s floodplain, south of Chipping Warden.

Two major new wildlife sites will be created where the viaduct crosses the floodplain, with fen, marshland and meadow alongside new woodland planting. The schemes, covering a total of 7.6 hectares, will create new habitats for insects, bats, newts and other amphibians.

The viaduct passes near the site of the medieval Battle of Edgcote, fought on 26 July 1469 during the Wars of the Roses. Historians believe that the battle took place on nearby Danesmoor. Archaeological investigation found no evidence of the battle at the viaduct construction site.

Steel and concrete production contributes significantly to carbon emissions, so HS2 expects the new, lighter-weight structure to save 360 tonnes of embodied carbon compared with the previous design, the equivalent of one person taking a flight from London to Edinburgh and back 1,865 times.

The new approach requires fewer lorries to deliver material , cuts waste and improves safety by reducing the requirement to carry out work at height. It particularly suits longer viaducts like Edgcote and Thame Valley.

Edgcote is one of fifteen viaducts designed by HS2 Ltd’s main works contractor, EKFB, which is a consortium of Eiffage, Kier, Ferrovial Construction and BAM Nuttall . They have worked with designer ASC, a joint venture between Arcadis Setec and COWI, and specialist architects Moxon. Both viaducts will be built by FC Civils Solutions, acting as EKFB’s specialist on-site construction partner.

Thame Valley and Edgcote viaduct designs have taken inspiration from recent high-speed rail projects in Spain, in which designers cut carbon by simplifying the structure of the viaduct so that every major element could be made off site.

HS2 is building more than fifty new viaducts, as part of a total of more than five hundred bridging structures. It has made significant progress at its other major viaducts over the last few weeks. Engineers have poured the first concrete for the approach viaducts for Birmingham Curzon Street station, installed the first beams installed at Thame Valley, and finished installing beams installation at Highfurlong Brook in Northamptonshire. Construction of what will be the longest viaduct in the UK, Colne Valley, recently passed the half-way point.

EKFB Project Technical Lead, Richard Smith, said: “As well as significant carbon savings, the redesign of Edgcote Viaduct also incorporates many health and safety benefits including less working at height and fewer temporary works associated with wet trades. There are also benefits to the local environmental such as reduced numbers of deliveries and activities on site, minimising the impact on local residents.“

Paul Cooper, HS2 Ltd’s Senior Project Manager, said, “Once complete, HS2 will transform journeys between London and the west midlands while freeing up space on the busiest part of the west coast mainline – but we’ve also got to deliver the key infrastructure in the most efficient way possible.

“The success of the Thame Valley Viaduct design shows that a two-beam approach can deliver dramatic carbon savings and speed up construction – particularly for longer viaducts – so it’s great that we’ve been able to roll it out again at Edgcote. ”