Health & Safety Executive (HSE) officials were this week preparing to investigate how a piling auger from a central London construction site penetrated and damaged a main line rail tunnel below.
Augers from mini piling work being carried out by contractor Andrew Towns-Wadey on a new seven storey, mixed use redevelopment scheme on East Road, close to Old Street station, broke through the tunnel lining last Friday.
Services on First Capital Connect’s Northern City Line route were suspended after a train driver reported seeing “muddy water” pouring into the tunnel just north of Old Street Station.
Two augers fell into the tunnel later the same morning as a Network Rail mobile operations manager approached to inspect the area in an empty train travelling from Moorgate.
Services were suspended to allow enquiries to be carried out by the Rail Accident Investigation Branch and British Transport Police.
Network Rail dispatched specialist tunnelling contractors to the scene to assess the damage and used the normal weekend line closure to undertake repairs.
The hole in the brick-lined tunnel, which was built in 1904, was plugged with a 1m thick concrete cap and plated over as a temporary repair to make the tunnel watertight and allow train services to resume. Grouting work to permanently repair the tunnel will take place this weekend.
The HSE said it was aware of the incident and that it would start its investigation this week. It has not ordered work on the construction site to stop.
The contractor declined to comment but confirmed that piling at the site at 99 East Road was linked to the Network Rail tunnel damage.