Species Protection | River Ashburn Fish Pass

National Highways
National Highways | 2022 | Staverton, Devon

An innovative leap for Devon’s river fish

As an experienced nature based services provider, we were delighted to be asked to work with National Highways to install a new fish pass on the River Ashburn in Devon. By selecting and managing contractors and ensuring no damage was done to the Site of Special Scientific Interest (SSSI) during construction, we demonstrated our ability to support nature positive interventions to mitigate the negative impacts of development.

Assisting fish migration

Salmon, eels and other species use the Ashburn Check Weirs to migrate during the autumn. They need assistance to make their way through the river, which runs through the Dartmoor National Park, a designated SSSI.

This migration process was being disrupted by four stepped weirs close to the A38 at Buckfastleigh. National Highways granted £450,000 from its Environment and Wellbeing fund to invest in a scheme to adapt the weir, allowing fish to migrate to their spawning grounds and to return to the sea.

Weir 3 Complete

A team-based approach

idverde was selected as the principle contractor by National Highways to rebuild three weirs and upgrade a fourth. Part of our remit was to find a specialist supplier with experience in installing the type of fish pass needed. We found a supplier – Castleford Engineering – which had exactly the right experience, and were also local – allowing us to invest in the local economy. We also worked alongside Fishtek, Kier Group, the West Country Rivers Trust and Castleford Engineering – a true team effort.

Temp works

Working within an SSSI

When working on an SSSI project, considerable time and thought goes into ensuring there is no damage caused to the site’s environment. This means considering everything from laying appropriate matting to protect the ground, to making sure there is no damage to protected habitats. This included working overnight to avoid disturbing roosting bats.

Our early works included tree and vegetation clearance around the structures and relocating plants before installing a temporary ground protection system to protect the SSSI verge which is one of the most important on the National Highways network.

Under idverde supervision our subcontractor installed temporary works to each weir – we needed to manage one weir at a time to avoid flood risk and water run off coming down from nearby moorland. Following successful installation of temporary works we demolished the old structures, which involved specialist concrete cutting equipment.

The concrete slopes were then re-profiled, followed by steel fixing and shuttering works. After concrete curing the new resin baffles and eel passes were created.

“This has been a fascinating and rewarding project to deliver. We were delighted to find a local contractor to support the work, and to have used our expertise to ensure there was no damage to the SSSI environment. We are delighted to have been able to support National Highways on this important project, and it reinforces the nature-based approach that we take to our work.”


“We’re delighted we could support such a worthwhile project which will help to support aquatic biodiversity close to the A38 - a glowing example of how this funding and partnership working can make life better for communities, wildlife and the environment around our roads.” “The investment underlines our commitment to reducing the impact of our roads on the environment – in this case by modifying a structure originally provided during the construction of the road.”