Spades in the soil as National Highways paves the way for Cornwall’s green bridge

As part of the major A30 Chiverton to Carland Cross dualling project, a dual-deck bridge has been constructed by contractors Costain over the new carriageway, with top soiling work now under way, turning the bridge from grey to brown, followed by ‘green’ planting in the autumn

Following the topsoiling and planting, the green bridge at Marazanvose will cater for a different type of traffic, providing a flourishing green border and a safe passage across the road for various wildlife species, including badgers, voles and other small animals, insects and birds.

The bridge – 49.3 metres in length and 12.5m wide – spans four lanes of the new dual carriageway and two lanes of the old A30, now the B3288, and will not only provide better connectivity for wildlife but also a footpath and a bridleway for horse riders.

Landscaping will involve the planting of two native hedgerows, with species including Hazel, Hawthorn, Holly, Dog Rose, Elder and Wych Elm, along with Hazel and Hawthorn trees and seeding of grasses and wildflowers, and ultimately will look similar to the visualisation below.

Green bridges – first built in France in the 1950s and pioneered in the Netherlands in 1990 – are now becoming an important part of the sustainability of infrastructure projects, by:

• creating a safe crossing point for wildlife movement;

• joining up habitats and connecting colonies, and making wildlife populations more resilient;

• creating a safe crossing point for people and improving road safety;

• integrating roads and railways into the surrounding landscape.

There are only a handful of green bridges across the country and for National Highways, it represents the third such structure to be built across the Strategic Road Network, and a second for Cornwall following Cormac’s construction of the A391 Carluddon road bridge for Cornwall Council.

The company, responsible for England’s major A roads and motorways, has already constructed green bridges over the A556 near Chester, the A21 at Scotney Castle in Sussex, while another green bridge is planned in the South West, as part of the A417 Missing Link scheme near Gloucester, and another at Cockrow in Surrey, as part of the M25 Wisley interchange scheme.

Andrew Alcorn, National Highways’ Programme Manager for the A30 Chiverton to Carland Cross scheme, said: “We’re really proud of the environmental work being carried out as part of this project, and the creation of the green bridge is a leading part of that.

“Our green bridge will be the third for the company, one of only a handful across the country, and once completed, it will provide a safe crossing for various species of wildlife, as well as for walkers and horse riders.

“Along with other environmental measures, we’ve built a total of 33 multi-species crossing points as part of the project, and we look forward to seeing the bridge bloom for many years to come, providing a real legacy for the scheme and for Cornwall.”

Material for the top soiling work has been sustainably generated from the scheme’s earthworks and around 960 tonnes of soil will be used across the bridge deck and embankments.

Planting work will take place in the autumn, along with seeding, and after all planting work across the scheme, a five-year maintenance period will follow to ensure the successful bedding in and growth of all new trees and shrubs.

As part of the road scheme, a total of 87,000 trees are being planted across the landscape, in addition to the green bridge planting, and with over 40,000 already in the ground, the remainder will be installed in suitable conditions later this year.

The new route has been designed to enhance biodiversity and improve connectivity for wildlife, with a total of 33 multi-species crossing points constructed alongside the new junction structures, to enable the journeys of animals such as otters, badgers, bats and reptiles, allowing access to a wider area of habitat.

As part of the environmental mitigation work, National Highways and principal contractors Costain are predicting an approximate 20% net gain in biodiversity.

Tara McCracken, Safety, Health and Environment Manager at Costain, said: “As part of a collaborative effort across the scheme we have placed a big emphasis on ensuring we are providing a positive legacy and delivering ecological and environmental benefits above and beyond what is required. We’re forecasting a biodiversity net gain of more than 20% across the scheme.

“The Marazanvose Bridge exemplifies this commitment and we’re very happy to now be making the final preparations on the structure to enable local wildlife to flourish and ultimately support a sustainable, decarbonised future for Cornwall and the surrounding areas.”

Initiatives to protect and improve biodiversity alongside the new route include the creation of eight miles of traditional Cornish hedging, as well as the restoration of existing hedging, the relocation of reptiles and a section of priority heathland habitat, over 28 miles of new drainage, the construction of a bat house, which is now home to a variety of roosting bat species, new filtration ponds, and the construction of earth barriers and sound-absorbing and wildlife-proof fencing.

As part of its Designated Funding programme, National Highways has also invested in Green Ribs projects to restore and recreate 16.8 hectares of woodland, orchard, grassland and heathland, and additional tree planting across the mid-Cornwall landscape, together with significant funding for Cornwall Council’s Saints Trails active travel initiative and Social Value funding to benefit local communities and charity organisations.

Mr Alcorn added: “Our work goes beyond the traditional focus of road investment and beyond building, operating, maintaining and improving roads, and through the scheme and other initiatives, we’re aiming to create a lasting legacy for Cornwall.”

Since opening the new dual carriageway to traffic last June, National Highways and principal contractors Costain have been progressing finishing works through the winter and spring, the work is now nearing completion and in the meantime latest updates on the scheme are available at National Highways' scheme web page.

The cost of developing the scheme has been funded by an £8 million contribution from the European Regional Development Fund, with an additional £12 million for the construction phase. The remainder of the cost of developing and delivering the scheme has been funded by central Government.

Notes to Editors

National Highways is the wholly government-owned company responsible for modernising, maintaining and operating England’s motorways and major A roads.

Real-time traffic information for England’s motorways and major A roads is available via the Traffic England website, local and national radio travel bulletins, electronic road signs and mobile apps. Local Twitter services are also available.

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