River Tay naturally. To aid this process and improve the health and resilience of the population a further 28 beavers will be released in Knapdale between 2017 and 2020, however there are no plans at present to release further beavers into the Tay. In the 19th century the Tay Rail Bridge was built across the firth at Dundee as part of the East Coast Main Line, which linked Aberdeen in the north with Edinburgh and London to the south. The bridge, designed by Sir Thomas Bouch, officially opened in May 1878. On 28 December 1879 the bridge collapsed as a train passed
Tay Bridge disaster were now constructed by sinking brick-lined wrought-iron caissons onto the riverbed, and filling these with concrete. To reduce the weight these had to support, Bouch used open-lattice iron skeleton piers: each pier had multiple cast-iron columns taking the weight of the bridging girders. Wrought iron horizontal braces and diagonal tiebars linked the columns in each pier to provide rigidity and stability. The basic concept was well known, but for the Tay Bridge, the pier dimensions were constrained by the caisson. For the higher portion of the bridge, there were 13 girder spans. In order to accommodate thermal expansion, at only