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Laigh Milton Viaduct
River Irvine, West Gatehead, Ayrshire, Scotland, UK
Laigh Milton Viaduct
associated engineer
William Jessop
date  July 1809 - July 1811
UK era  Georgian  |  category  Railway Viaduct  |  reference  NS382369
ICE reference number  HEW 1469/01
photo  courtesy Roland Paxton
Laigh Milton Viaduct, also known as Milton Bridge or Gatehead Viaduct, is believed to be the world’s earliest surviving viaduct on a public railway. It was built by William Jessop for the Kilmarnock & Troon Railway, Scotland's earliest line. The viaduct was in use until 1846. It later fell into disrepair but was restored in 1995-6 when a replica of the original track was reconstructed on it.
The Kilmarnock & Troon Railway was built for the railway company’s chairman William Bentinck (1768-1854), fourth Duke of Portland, for the transportation of coal from west of Kilmarnock to Troon Harbour (NS307315). It was a double track cast iron plateway, with wagons drawn by teams of horses.
The viaduct is about 82.3m long and 5.8m wide overall. It carried the railway’s tracks some 7.6m above the River Irvine on four 12.2m span local freestone segmental arches. The three 2.7m wide piers have rounded cutwaters with buttresses to parapet level, and were erected inside cofferdams.
Laigh Milton Viaduct was closed in 1846 and bypassed in 1847. Scottish railway engineer John Miller (1805-83) directed the upgrading and re-alignment of the Kilmarnock & Troon Railway, which carried the refurbished line over the river on a timber viaduct (NS383368, now demolished) just upstream (to the south). The timber structure was in turn bypassed by the present operational railway viaduct (NS382365) in 1865, located even further south.
Laigh Milton has been a Category A listed structure since January 1982. By 1992, its stone was crumbling and it was near collapse. The westernmost arch had sagged and the adjacent one had hogged. Part of the east side of the west pier had disintegrated and there were cracks up to 60mm wide in the superstructure.
Its historical significance led to the formation of the Laigh Milton Viaduct Conservation Trust in February 1992. The directors raised over £1m, purchased the viaduct for just £2, and oversaw its restoration. This began on 5th June 1995 and was completed in 1996 within budget on a design-and-build contract basis by Barr Ltd. The project was funded (in descending order of grants) by the National Heritage Memorial Fund, Historic Scotland, the European Union, Kyle & Carrick District Council, Strathclyde Regional Council, Kilmarnock & Loudoun District Council and Enterprise Ayrshire.
The restoration work involved temporarily damming the river, using steel centring frameworks to support the extrados of the arches, stabilising the piers, strengthening the spandrels and constructing a new deck. Defective masonry was replaced and the structure was pointed with lime mortar.
On excavation of the deck, the outer walls were found to be acting as gravity retaining walls with boulder clay infill between, rather than having hollow cross-tied spandrels. They derived some lateral support from the bull-nosed buttresses above the piers. The freestone masonry elements had weathered much more than the harder stone of the pier bases.
Investigations during reconstruction showed that the west pier was founded on a timber platform 127mm thick about 1.8m below normal river level, resting on sand, gravel and weathered bedrock. The other two piers probably have similar foundations.
Railings and copings were provided along the edges of the viaduct for safety, though originally it would not have had any, and cast iron interpretive plaques were attached to the railings.
A short length of replica 1.22m gauge plateway was constructed using the same pattern as a Kilmarnock Foundry rail found on site in 1995. These were 910mm long and pinned together at each end by an iron spike driven into a wooden plug within a stone block. Curved upstands next to the wheel track acted as guides and added strength. The 'horse path' is of broken stone.
Historic railway ironwork from the refurbishment is now on display at the ICE Museum at Heriot-Watt University and at the Dick Institute, Kilmarnock, which also has a fine oil painting of the Kilmarnock & Troon Railway in operation during the 1830s.
The viaduct officially re-opened on 29th October 1996. Ownership was transferred to East and South Ayrshire Councils on 18th April 1997. It is now owned and maintained by East Ayrshire Council Roads Department and can be reached via a footpath near Laigh Milton Mill (NS382373).
Resident engineer: Thomas Hollis
Contractor: John Simpson
Reconstruction engineer (1995-6): Barr Technical Services
Reconstruction (1995-6): Barr Construction
Temporary arch support and railings (1995-6): Solway Engineering
Research: ECPK
"The Laigh Milton Viaduct Restoration Project" by Joe Meagher, in Construction Repair, Vol.11, pp.30-32, Palladian Publications Ltd, Elstead, 1997
"Conservation of Laigh Milton Viaduct, Ayrshire" by R.A. Paxton, in Civil Engineering, Vol.126, pp.73-85, ICE Proceedings, London, May 1998
reference sources   CEH SLB

Laigh Milton Viaduct