The wide and deep cutting to the south of Malahide station provided much of the stone required to build the embankment northwards across the estuary to Donabate in the early 1840s. The viaduct, known locally as ‘The Arches’, was originally built in 1844 and, together with the embankment, greatly changed the ecology of the estuary. The original was a remarkable structure built entirely of wood, comprising eleven spans of 50 feet length. In 1860 a new iron bridge was built but they kept trains running during construction. The engineer in charge had a special castellated stone office built for his use and this can be seen today at the northern end. 90,000 tons of stone were discharged along the line of the bridge to overcome the scour produced by tidal currents. 8,000 tons had to be replaced after severe storms in 1922 and 1965. The viaduct was again replaced in 1966/67 with a wholly pre-cast scheme involving 2,100 tons of concrete units and including 43 miles of pre-stressing strand wire. This was believed to be the largest pre-cast superstructure in Ireland at the time. The work was carried out on Sundays at a cost of £83,000 but this time there was disruption to services with passengers being bussed from Malahide. Until Friday 21 August the viaduct had 12 spans, not all of equal length, and it is 577 feet in length.