Why is it costing £1.5m to investigate mine shaft under tram tracks?

An old mine shaft has opened beneath the outbound Sheffield Supertram track at Birley Lane, forcing the suspension of services between Gleadless Townend and Halfway. Emergency investigation and repair work is now expected to cost about £1.5m, and the blue route’s reopening date is unknown.

The track ballast fell into a void on 23 August, leaving sleepers and rail unsupported. Engineers are investigating the shaft, with drilling permits allowing work to reach 60 metres; officials say they have yet to establish what the feature is or what repairs it will need. An engineering academic said Sheffield has many historic mine workings and that shafts can be hard to detect, while replacement buses have faced overcrowding.