Two 18 metre-long bridge beams, each weighing 1.7 tonnes, were lowered onto prepared foundations with 25mm precision.
The bridge has been replaced four times since the Maentwrog dam began generating electricity in 1928. Its runs between the plant’s two high pressure pipelines that surge 4,000 gallons a second driving the two turbines below.
Maentwrog manager Andy McAteer said: “Weather conditions were near perfect for the operation and it was mesmerising to watch the helicopter pilot skillfully lift the bridge beams into position between the pipelines. It is a great credit to our supply chain partners, Mona Lifting and Heli-Lift Services, for their extensive planning to ensure the installation was successful.”
The design and fabrication of the footbridge took six months at the Mona facility in Anglesey. This included a mock-up and full trial air lift to ensure dimensional accuracy and slinging trials to guarantee that all the components could be safely lifted by helicopter.
Mona Lifting operations manager Gethin Jones said: “A team of 12, including two apprentices, worked on this unique project which began with a 3D dimensional scan of the site to ascertain the abutment points the new bridge would be attached to. We reformed one of the degraded abutments, erected scaffolding for site access and removed the former wooden structure.”
Maentwrog power station is operated by Magnox on behalf of the Nuclear Decommissioning Authority. It is Magnox’s only hydro-electric plant.