The Barmouth, North Wales railway viaduct restoration is being carried out by Alun Griffiths and Network Rail, the train operator. Pennys Group has been contracted to demolish the old viaduct.
“Many of the timber elements of the viaduct have decayed significantly over time and a large proportion of the metallic elements have corroded,” Network Rail, which is carrying out the work, said.
Metal sections of the bridge will be reconstructed and tracks renewed on the northern edge of the viaduct, which means two 160-tonne metallic spans will have to be removed. Network Rail has carried out a mock manoeuvre to streamline the process before it is carried out, it says. Fifteen engineers tested the cantilever and jack system, 16 of which had to be used to lift each span.
More than 500m2 of floating scaffold has been provided by pontoon firm ScaffFloat, which will be used to catch the bridge sections when they are lowered and tow them to the beach for demolition.
“We mobilised on the beach, building four heavy-lift pontoons, 12m x 8m, with 63 large floats giving 63m3 or 63t of buoyancy,” says ScaffFloat. “To push/ tow them around we have two ScaffFloat Workboats, an 8m x 4m with two high-thrust Yamaha outboards giving 0.8t bollard pull, and a larger 8m x 6.4m with two high-thrust Yamaha 100hp outboards giving 1.5t bollard pull.”
A spread of anchors has been laid either side of the bridge, attached to deck winches, which are also attached to bridge piers to hold the pontoons in place.
“The big challenge here is weather and tide giving us small windows around slack water to perform the lifts,” says ScaffFloat.
“To reduce the impact of our work, we’ve carefully planned for it to take place over several years,” says Network Rail. “Our programme will see us completely restoring the viaduct in a way that doesn’t threaten its industrial heritage and its Grade II listed status. This means that we will replace its components on a ‘like-for like’ basis so that it retains its magnificent appearance. We will be carrying out additional work during our £30m restoration to the iconic landmark, including replacing all the timber main beams.”
