Black Bridge

SSE’s new substation at Fanellan needs a 275-tonne transformer delivered to site, and the only river crossing on the route is life-expired, in too poor a condition to take a load anywhere near that size. Without a new bridge, the transformer can’t get there and the project can’t be completed. DYSE is supporting Beaver Bridges with the full design of its replacement: a 90-metre single-span structure stretching across the River Beauly, in a remote section of the Highlands were the landscape, river and access all shape what’s possible. 

The new Black Bridge will be two traffic lanes and a maintenance footway, with a concrete deck designed for heavy abnormal loads. DYSE is delivering both the superstructure and substructure design. 

Two requirements made this more than a standard span: the bridge has to be launchable across the river, built on one bank and pushed into position, and it has to be removable from beneath the old bridge without taking the crossing out of action. On top of that, the design allows for bearing replacement in future, again without closing the bridge. Each of those is a meaningful constraint on its own; designing for all three together is where the real engineering judgement comes in. 

DYSE’s scope runs from feasibility and outline design through to detailed design, Category 3 check liaison and construction-stage support, including early surveying, preliminary sizing, 3D modelling and geotechnical investigation to inform foundations and approach works. We’re working with BAM, Beaver Bridges and Fairhurst, who lead the overall programme, alongside the temporary works designers and local stakeholders. 

The combination of a long span, an accelerated timeline and the launch sequence has put this project at a very high design risk rating, with every decision made has to pass multiple levels of scrutiny. 

Once installed, Black Bridge removes a long-standing pinch point for the local community and gives residents, visitors and service vehicles a dependable crossing while also being the piece of infrastructure allowing a nationally significant energy upgrade to actually happen on site. It’s designed to stay in service through future maintenance, so it keeps working for the area long after the transformer has passed over it.