Piling on the £445M M74 extension in Glasgow was halted last week after cracks and falling plasterboard were discovered in one of the tunnels in the city’s subway system.
Rig operators had been installing bored piles just 25m away from the subway line on the project, which will complete the missing link between the M74 and the M8 motorway. Glasgow subway operator Strathclyde Partnership for Transport (SPT) withdrew consent for further piling works near West Street subway station when the cracks were discovered.
Since January the Interlink M74 joint venture of Balfour Beatty, Morgan Est, Morrison Construction and Sir Robert McAlpine had been carrying out piling work for the Port Eglinton Viaduct. At West Street bored piles were being installed for the viaduct’s west abutment and its piers. An SPT spokesman said the investigation was ongoing but added: “It is very interesting that we had no problems before the piling work started.” Maintenance engineers were carrying out routine daily inspections on the tunnel near the West Street station, near to the M8, in the early hours of 5 March when they discovered the damage and plasterboard debris.
Most of the subway service was badly affected while SPT engineers closed the tunnels and carried out inspections for further damage. It eventually fully re-opened at 5pm. SPT said Interlink M74 would be taking responsibility for an investigation into what caused the damage. “Our engineering consultants are working with the contractor, Interlink M74 to reach agreement on what engineering measures need to be put in place to ensure that piling can continue while ensuring the integrity of subway tunnels,” said the spokesman.
A spokesman for Interlink M74 said that piling would continue elsewhere on the project but that it would be monitored closely. The new 8km motorway will have three-lanes in each direction plus hard shoulders. Construction began in May 2008. A Transport Scotland spokesman said the programme was still on schedule to meet its 2011 deadline.