Cornwall’s concrete green bridge nears completion
A concrete bridge designed to support both local wildlife and rural connectivity is nearing completion on the A30 in Cornwall, where Costain is delivering the Chiverton to Carland Cross dualling scheme for National Highways.
Known as the Marazanvose green bridge, the 49.3 metre-long, 12.5 metre-wide dual-deck structure spans both the new dual carriageway and the old A30 (now the B3288), providing a safe crossing for pedestrians, horse riders and a variety of wildlife.
The bridge forms part of a wider effort to enhance biodiversity and reduce habitat fragmentation in the region. Topsoiling works are currently under way, with 960 tonnes of soil—reused from the scheme’s earthworks—being placed across the bridge deck and embankments. Planting is scheduled for the autumn, including native species such as hazel, hawthorn and wildflowers, with National Highways forecasting a 20% net gain in biodiversity across the route.
Tara McCracken, safety, health and environment manager at Costain, said: “We’ve placed a big emphasis on ensuring we’re delivering ecological and environmental benefits above and beyond what’s required. The Marazanvose Bridge exemplifies this commitment.”
The bridge is one of 33 multi-species crossing points included in the nine-mile A30 upgrade, which also features a specially constructed bat barn, new filtration ponds, and more than 40,000 newly planted trees to date.
Andrew Alcorn, programme manager for the A30 scheme at National Highways, added: “Once completed, this will provide a safe crossing for various species of wildlife, as well as for walkers and horse riders. It’s a real legacy project for Cornwall.”
The bridge uses a concrete deck structure that supports both landscaping and live loads, demonstrating how concrete infrastructure can be adapted to deliver environmental benefits in line with sustainable transport and habitat restoration goals. Since traffic was switched onto the new dual carriageway in mid-2024, Costain has been completing final works across the project, which is now entering its final phase.
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