“If the whole viaduct is going to have to be rebuilt, it could be massive undertaking”

While Iarnród Éireann are still predicting it will be “at least three months” before the line across the Broadmeadow viaduct near Malahide reopens, following its collapse on Friday, Translink are already talking of the line closure lasting “6 months or more”. That seabed erosion, possibly in recent weeks, is being suggested as the cause of the collapse, might point to a problem with the location itself. As the Irish Times Environment Editor, Frank McDonald, details, the viaduct has been rebuilt completely on a number of occasions since the first timber structure was built by the Dublin and Drogheda Railway in 1844. It was last “replaced in the period 1966-1968 with the current prestressed concrete structure”.From Frank McDonald’s report

THE VIADUCT over Broadmeadow Estuary has given trouble since it was first built by the Dublin and Drogheda Railway in 1844, mainly due to tidal scouring of its support piers. Indeed, the first structure – made entirely of timber – had to be replaced by wrought iron superstructure on stone piers as early as 1860.

As engineer Niall Torpey recounted in the Irish Railway Record Society’s journal, the superstructure had to be strengthened to carry heavier locomotives on the Dublin-Belfast line in 1932. The stone piers also needed regular attention because of Broadmeadow’s tidal scouring and were repointed in the 1960s.

“Finally, following the observed deterioration in the wrought iron in this marine environment, it was further replaced in the period 1966-1968 with the current prestressed concrete structure”, Mr Torpey wrote. Since then, no further major works were carried out on the viaduct, which is 180m (594ft) long.

In 1998, as Fine Gael transport spokesman Fergus O’Dowd recalled yesterday, International Risk Management Services (IRMS) identified sections of the viaduct as being among the most unsafe stretches of rail track in the country, assigning it a 60 per cent security risk on a scale where 5 per cent is “best practice”.

The IRMS report led to a major improvement in railway standards, including relaying track on precast concrete rather than wooden sleepers. Two follow-up reports, also by IRMS, in 2001 and 2003 monitored the progress on what Barry Kenny, spokesman for Iarnród Éireann, called “this massive investment programme”.

And from the Irish Times report on the viaduct’s collapse

Iarnród Éireann said a preliminary examination showed a small breach occurred in the seabed, possibly in recent weeks, which changed the flow and pressure of the water around the viaduct piers.

“Recent low tides, coupled with major rainfall on Wednesday, would have seen the volume and speed of water flowing out of the estuary increasing, causing water pressures to increase, with ultimately the forces of water pressure widening the breach quickly,” said Barry Kenny, Iarnród Éireann spokesman.

“The effect on the causeway plateau and sea-bed would ultimately result in the sudden and catastrophic undermining of the pier supports from below water level, resulting in the collapse of the pier on Friday evening.”

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  • Framer

    Looks more like metal failure than erosion from the picture.

  • Davros

    The Aircoach people must be crying tears of joy.

  • Mick Fealty

    That’s forty years without a substantial rebuilding of the structure. Considering the previous gap was more like 30, it looks like serious maintenance was overdue, given the conditions at that point in the estuary. You’d kind of hope that like the airlines that Irish Rail are instigating an immediate and comprehensive safety check of the whole network.

    Nice PR switcheroo from the company which actually has to carry passengers on by crowded coach from Drogheda into Dublin (ie more than three months). With a seriously complex structural problem it could be a lot more than six.

    Grim times ahead for commuters.

  • Mick Fealty

    Not to mention a tidy sum to be added on to the capital expenditure bill…

  • Pete Baker

    Mick

    The more I think about it, the more concerning the reported rapid deterioration of the seabed, through erosion, is.

    If the current structure is vulnerable to a few weeks erosion then producing a safe viaduct at this location would require a major civil engineering project.

    That would require a re-evaluation of the environmental factors before any plans could even be drawn up.

  • Danny O’Connor

    Sabotage by those trying to cut north/south links:)

  • Then there’s this logistical problem:

    Had it occurred at night, the company would now be faced with a severe logistical problem as nearly all of the suburban commuter trains are housed in the new maintenance depot at Drogheda station.

    “We have 44 carriages there that can’t now be used on the rest of the network,” Mr Kenny said. “That’s 44 out of a total of 180, so it means that other services can be met” – on the Maynooth, Kildare and Gorey lines. Two of the four Belfast Enterprise trains were north of Malahide, which means they can be run to and from Drogheda.

  • If the government hadn’t dragged their feet appallingly on Clonsilla-Navan, trains could be routed from Drogheda Depot to the rest of the network – laborious obviously, but it could be done. The Bray Head landslip was a warning shot as to the lack of resilience in the Irish railway system (hardly a “network”) and this is the full cannon blast.