Scottish viaduct gets sensitive treatment from National Highways

The masonry repairs of the arch soffit were carried out from cradles and by rappelling in the voussoirs.

As the video below shows, the 16-arch viaduct that straddles the River Avon on the border of West Lothian and Falkirk has been returned to its former glory thanks to a £2m renovation program funded by Historical Railways Estate (HRE).

Work on the Westfield Viaduct included masonry repairs, waterproofing, and the installation of 19 bat bricks, six bat tubes, and two bat boxes. It took 18 months to complete and you should see the structure, built in the 1850s, standing for a few more generations.

HRE civil engineer Colin McNicol said he was pleased with how well the job had gone. “The viaduct had numerous issues that required attention to ensure it remains safe and in good repair, and the work that has been completed makes any future plans to reopen the viaduct as an active travel route for pedestrians, cyclists and other users a must. real possibility”. he said.

Westfield Viaduct is among 3,100 former railway structures maintained by the National Highways Historical Railways Estate (HRE) on behalf of the owners, the Department of Transport. Despite the fact that National Highways has no remit for highways in Scotland, which is a delegated matter of the government, it still deals with rail viaducts that are no longer in use.

Westfield Viaduct was built between 1854 and 1855 as an extension to the Monkland Railway. This branch line ran from Blackston Junction on the Slamannan Railway to Bathgate to meet the Wilstontown, Morningside and Coltness Railway before turning west to go to the mines around Crofthead before becoming part of the North British Railway in 1865.

The structure has 12 large arches with a span of about 47 feet and two small ones at each end. In total it spans 660 feet over land and water and rises 60 feet from the top of the arch to the river bed.

Before renovations could begin, two rounds of bat surveys were conducted at different times of the year, including a summer re-entry survey to ensure bats had not returned to work areas to hibernate. The surveys included rappers under the direction of licensed bat ecologists who checked cracks in the masonry with endoscopes (a long, thin tube with a camera inside) for signs of bat activity. Drones were used for more controls.

All cracks that showed signs of bat droppings or dark spots on the stones, and cracks that were too difficult to properly inspect, were fitted with excluders that allowed bats to exit but not re-enter. All surveys were completed using a NatureScot bat license.

Temporary bat boxes, tubes and bricks were installed in areas of the structure where work was not taking place for safe use by bats during the hibernation season. Multiple bat bricks, boxes, and tubes were then built into the viaduct as permanent bat roosts.

Related information

Other works included extensive vegetation removal and repairs to all 16 spans, along with north and south parapet repairs and waterproofing work. New cast iron kick plates, fabricated to match the originals, were also installed to replace damaged items and stone repairs were color matched to the original unworn material.

The National Highways HRE team often come under fire in the media for somewhat clumsy shortcuts in maintaining their Victorian bridge, simply filling the voids under the arches with rubble and concrete, thus preventing any development of greenways along it. along the disused railway alignments under the arches.

In June last year, the former chairman and chief executive of the Strategic Rail Authority, Richard Bowker, was so outraged by what had happened on the Great Musgrave Bridge in Eden Valley in Cumbria that he said: ‘I’ve never really liked it’ and now heads should roll’ but, at least this time around, the CEO of National Highways should formally apologize and scrap this policy of unwarranted vandalism.”

Replacement of the plates of the patres

New cast iron voussoirs and plates, cast to match the original ones
New cast iron voussoirs and plates, cast to match the original ones

Millar Callaghan Engineering Services was awarded the contract to replace the damaged and broken brace plates and braces that hold the structure together at the top of the 16 arches.

Close inspection determined that the detailed dimension and design of the existing steel cast iron plates would exactly match the new replacement plates. The new plates and stays were made in Millar Callaghan’s Irvine shop.

A spider crane was placed on top of the viaduct to assist with the removal of the old plates and the installation of the new ones. Powered access platforms were used to access both the exterior face and the underside of the arch for removal and installation of steelwork.

The old cracked and damaged plates that were removed were carefully and skillfully removed to ensure they would not break during removal. The new plates and stays were then installed and tightened into position. A fresh coat of paint was applied to refresh both the new and existing steelwork.

Do you have a story? Email

Leave a Comment