The Lamington Viaduct is a four-span railway bridge that crosses the River Clyde at an angle, a mile (1.6 km) southwest of Lamington. At 101m / 331 feet in length, this is the longest of the four bridges which carry the West Coast Main Line railway over the Clyde. The line lies at around 4m / 13 feet above the water level. Built in 1863 to replace a timber viaduct which had carried the Caledonian Railway since its opening in 1848, it comprised a flat deck supported on three 15-m / 49-foot long sandstone masonry piers. In 1936-38, each of these masonry piers were extended by a further 13m / 43 feet downstream in concrete to widen and strengthen the structure so as to support a new straighter deck that allowed faster train speeds. This resulted in over-wide piers, only part of which were now required to support the deck. In 1999, the old deck was replaced once again permitting a further increase in speeds as part of the West Coast route modernisation project. This new concrete deck is supported on steel bearings which allow movement associated with thermal expansion. Access walkways in steel are attached to either side of the deck.
There was always concern that the piers were at risk of undercutting by the fast-flowing river and following Storm Frank's widespread flooding and disruption to Scotland on the 30th December 2015, the Clyde reached its highest-ever recorded level of 3.12m / 10.2 feet above datum. After a train reported a dip in the track over the viaduct, a maintenance team discovered that a pier had lost structural integrity and the bridge was closed to all traffic for two months. Remedial measures included improved anchoring of the piers, pouring 400 cu. m of concrete, adding 17,000 tonnes of rock armour protection, lifting the bridge deck to install replacement bearings and bank protection measures upstream to protect both approach embankments. This work was undertaken by Yorkshire-based AmcoGiffen on behalf of the viaduct's public-sector owners Network Rail.
The restoration works were awarded a commendation at the Saltire Awards of 2016 for 'the greatest contribution to civil engineering' which not only brought back into service a failing railway bridge but re-opened a crucial transport artery. The Rail Accident Investigation Branch subsequently criticised Network Rail for limitations in their inspection procedures for vulnerable structures.
