In March 2002, a collapse adjacent to the south portal of Whitrope Tunnel deposited tonnes of rock onto the trackbed of the former Waverley line, the much-missed cross-border link between Edinburgh and Carlisle. More minor falls have increased the size of the debris heap over the subsequent 20 years.
This tunnel section was historically a cause for concern, and engineers had already installed a series of strengthening ribs to provide additional support. But they needed to be in a better place, allowing the lining to fail.
Recently another significant collapse of material has resulted in the tunnel being wholly blocked and a hole appearing through which daylight can be seen.
Any reuse of the tunnel as part of an extension to the Borders Railway will now require reconstruction of the southernmost 30 metres.
Those who have been inside the tunnel over the past few weeks report that the blockage has resulted in a loss of air flow and low oxygen levels. The structure should therefore be regarded as dangerous.
Whitrope Tunnel was arguably the most significant structure on the Border Union Railway. It opened in 1862 and is Scotland’s fifth-longest railway tunnel at 1,208 yards.
600 navvies worked on construction at its peak, sinking five shafts from the bleak moorland above.
400 gallons of water gushed into the workings every minute.