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Rhigos Road Rockfall Protection

Crossing the dramatic landscape of South Wales, the Rhigos Road links the communities of Treherbert and Hirwaun through a steep mountain pass. When a fire damaged the existing plastic-coated netting along a section of the cliff, it became clear the rockfall protection system needed an overhaul.

The steep topography presented major challenges. Our infrastructure team responded with an innovative design that challenged the UK¡¯s conventional approach to rockfall mitigation. We adopted a hybrid system more commonly used to deal with avalanches in Alpine regions.

Rather than cover the entire 70-metre (230-foot) cliff face in netting, we developed an alternative option, including the UK¡¯s first use of Geobrugg attenuators. Positioned at strategic intervals, the attenuators dissipate rockfall energy while allowing debris to be caught at the roadside. These systems, combined with high-capacity barriers and high-tensile tecco and spider netting, provided robust protection while dramatically reducing the construction footprint.

By treating only the lower 25 metres (82 feet) of slope, we saved time and reduced costs while improving safety. Using digital tools throughout research and design stages, we prioritised working on the road safely, protecting workers, and reducing disruption to the travelling public.

Rhigos Road has become more than just a safer route. It has set a precedent for the future of geotechnical resilience over challenging terrains. The project was completed seven weeks ahead of schedule and delivered significant carbon savings. In 2025, this project was highly commended as a UK Project (between ?1-3 million) at the Ground Engineering Awards.