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Rail culvert collapse triggers safety fears

Poor maintenance and a lack of rigour in recording the condition of small, safety critical rail assets has been highlighted in a report on the collapse of a culvert under a railway line near Bromsgrove, accident investigators said last week.

The Rail Accident Investigation Branch (RAIB) report into the collapse said a lack of knowledge is reported to have been the main cause of the partial collapse of the culvert known as Bridge 94 last year.

The RAIB report said the partial collapse occurred because of the combination of a failure to inspect the structure after 1993 and the fact that inspectors carrying out weekly track checks were unaware of the structure and the location of an adjustment switch in the rails directly above.

The 47m long single span brick arch culvert was reconstructed on stone abutments in 1931 to allow the Bromsgrove Stream to pass below the railway line to the south of Bromsgrove station.

No inspections

Records show that confined space working and the potential for noxious gases prevented consultant Owen Williams Railways, and later Amey, which took over Owen Williams in 2006, from making internal inspections of Bridge 94 and that no other action was taken to inspect the structure.

Subsidence of the track ballast was noted during a routine track level inspection on 22 March 2011 and the engineer called for the track to be lifted and packing of the ballast to be carried out within four weeks.

Further inspections on 29 March and 5 April that year also noted subsidence and resulted in ballast being replaced. Neither of the engineers involved in these inspections knew about the ­structure.

The ballast was found to have collapsed further on 6 April, and the Network Rail assistant track section manager on site located the culvert, which he believed was causing the subsidence.

The track was monitored during the day and line speed restrictions put in place before trains were diverted onto other lines when it became clear that the collapse was progressing with each passing train.

Emergency repairs enabled services to be restored within 36 hours.

The RAIB believes that the issue of unknown or uninspected culverts could be widespread on the UK rail network.

Limited information

“Network Rail has limited information on culverts and pipes of 900mm or less, as many of the records relating to these structures have been archived or lost, and the information is often missing from route plans, despite the fact that many are track-supporting,” said the report.

According to a Thames Water report, a study of structures under railway lines - for which Network Rail is legally responsible if they pre-date the railway - showed that up to 70% of small brick culverts (350mm to 750mm) are in very poor condition.

The report found that 50% of clay pipes (525mm to 600mm diameter) were also in poor ­condition.

The RAIB report concluded that unidentified and/or unmarked structures are an unknown risk to the safety of the operational railway.

Amey said it was unable to comment on the report. Network Rail was approached for a comment but had not made one as NCE went to press.

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