Thursday 8 December 2016

Rail chiefs had been warned of viaduct erosion

Fears raised three years before shock collapse

Published 11/03/2010 | 05:00

IARNROD Eireann was warned about serious erosion on one of the country's busiest commuter lines three years before it collapsed into the sea, the Irish Independent has learned.

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A survey of the seabed in 2006 found evidence of serious erosion around the pillars supporting the Malahide viaduct.

But Irish Rail failed to heed the warning because its engineers did not understand how the viaduct structure worked, the rail company's report into the incident reveals.

The revelation raises serious questions about the safety of our railway network.

Iarnrod Eireann was forced to launch an investigation into the safety of 105 bridges after the near-catastrophic collapse of the Malahide viaduct last August.

The specialists examined the foundations and structure of each bridge, and all were deemed safe.

However, the report into the collapse of the Malahide viaduct has highlighted serious new concerns about the company's safety culture. It is unclear why basic engineering details about one of the most heavily used lines in the country were lost.

The report found that the seabed was being washed away from at least 2006, undermining the foundations of a pillar that supported the track.

Engineers failed to realise that the viaduct's foundations had to be maintained because the knowledge had been lost as staff retired or moved to other positions in the company.

The report said: "The collapse of the structure was due to the undermining of one pier's foundation caused by 'scour' erosion."

It added that there was evidence some channels under the piers supporting the viaduct had been significantly deepened. "This is indicated in the 2006 scour inspection report."

The findings contradict evidence given by company officials to the Dail transport committee last September. Chief executive Richard Fearn then told TDs and senators: "That survey (2006) showed no evidence of scour (erosion) and gave a clean bill of health for the following six years."

But the 2006 survey said, like all bridges in water, the structure was prone to erosion. And it found that the seabed was being eroded near the support pillars -- a finding that should have set alarm bells ringing.

But inspectors wrongly assumed the pillars that held up the track were sunk into the bedrock rather than resting on a man-made causeway, which was being gradually eroded.

The Irish Rail report found:



  • There was evidence of the channels between Piers 4, 5 and 6 being "significantly deeper" than the channels between the other piers.
  • It was "likely" in 2006 that the bottom of the channels were "at or below" the foundation level of the adjacent piers, albeit some distance away.
  • Maintaining the causeway was of "paramount importance" to ensure the integrity of the viaduct, but it was "no longer fully appreciated".
  • The collapse was caused by the "undermining of one pier's foundation caused by scour erosion".


Structure

The report concludes that the emphasis was on maintaining the viaduct structure, and not the causeway.

It added: "The importance of maintaining the weir profile was no longer fully appreciated."

This lack of appreciation could have resulted in massive loss of life.

On August 21 last year, erosion caused a supporting pillar -- Pier 4 -- to begin to collapse into the sea as a packed commuter train passed over it and tragedy was only narrowly averted.

Iarnrod Eireann last night admitted safety staff had not known the foundations of the viaduct needed to be maintained. A spokesman said: "Our focus now is on learning from the key lessons of this most serious accident."

Irish Independent

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