Scottish viaduct gets the sensitive treatment from National Highways

National Highways’ restores Victorian viaduct.

Masonry repairs to the arch soffit were undertaken from cradles and by abseilers on the voussoirsAs the video below shows, the 16-arch viaduct that straddles the River Avon on the West Lothian and Falkirk border has been returned to its former glory thanks to a £2m renovation programme 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 should see the structure, built in the 1850s, stand for a few generations more.

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

Westfield Viaduct is among the 3,100 former railway structures maintained by National Highways Historical Railways Estate (HRE) on behalf of owners, the Department for Transport. Even though National Highways has no remit for highways in Scotland – that is a devolved government matter – it still looks after railway viaducts there that are no longer in use.

Westfield Viaduct was constructed between 1854 and 1855 as an extension of 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 ran to mines around Crofthead before becoming part of the North British Railway in 1865.

The structure has 12 large arches of about 47ft span and two small ones at each end. In total it stretches for 660ft over land and water and stands 60ft from the top of the arch to the riverbed. Before renovations could begin two rounds of bat surveys were carried out at different times of year, including a summer re-entry survey to ensure bats had not returned to work areas for hibernation. Surveys included abseilers under the direction of bat-licenced ecologists checking crevices in the masonry with endoscopes (a long thin tube with a camera inside) for signs of bat activities. Drones were used for further checks.

Any crevice that showed signs of bat droppings or dark stains on the stones, and crevices that were too difficult to survey properly, were fitted with excluders that allow bats to leave but not re-enter. All the surveys were completed under a NatureScot bat licence.

Temporary bat boxes, tubes and bricks were installed on areas of the structure where work was not taking place for bats to use safely during the hibernation season. Multiple bat bricks, boxes and tubes were then built into the viaduct as permanent bat roosts. Other work included extensive vegetation clearance and repairs to all 16 spans, along with north and south parapet repairs and waterproofing work. New cast iron pattress plates, manufactured to match the originals, have also been installed to replace damaged elements and stone repairs were colour matched to the original unweathered material.

National Highways’ HRE team is usually under fire in the media for somewhat cackhanded shortcuts in its Victorian bridge maintenance, simply filling in voids beneath arches with rubble and concrete, thus preventing any development of greenway routes along the disused railway alignments beneath the arches.