bri - Bont Briwet Newydd

This pair of modern concrete viaducts, carrying road & rail routes across the Afon Dwyryd.
Which replaced a grade II listed wooden viaduct, which was demolished in 2013 [after it was rumoured that proposals to keep the road section for pedestrians / cyclists had been accepted].

en.wikipedia.org/wiki/Pont_Briwet

during construction work, there were incidents of scouring to the river bed, and partly as a result of that erosion, pylons had to be demolished.