[ThomasJ]

Independent
http://www.independent.ie/national-n...r-1868289.html

By Paul Melia


Tuesday August 25 2009

TRANSPORT Minister Noel Dempsey has ordered Iarnrod Eireann to carry out an urgent safety review of all viaducts and bridges which run across open water on the rail network.

And the rail company last night revealed that a preliminary investigation had identified erosion of the seabed as a possible reason for the collapse of a 20-metre section of the railway viaduct near Malahide, which has left thousands of commuters without a train service.

Investigators are now focusing on "recent and significant erosion of the seabed" as inspections of the viaduct in 2006 and 2007 found that it was structurally sound.

Heavy rainfall, coupled with low tides, may have seen water pressure increase on the bridge, which could have then caused the collapse.

Pressure

"It is believed that in a relatively short time-frame, possibly in recent weeks, a small breach occurred in a causeway plateau within the seabed. This would have resulted in changes to water flow, with increased water pressure on the area," the company said.

"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. . . The effect on the causeway plateau and seabed 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."

Thousands of commuters are facing disruption for at least the next three months, with services to Balbriggan, Skerries, Rush, Drogheda and intercity services to Belfast affected.

Iarnrod Eireann's investigation will also examine tidal issues in the estuary, rainfall and climatic issues and inspection and maintenance procedures, and last night it said it would undertake a "detailed inspection" of bridges and viaducts across areas of running water.

This comes after Mr Dempsey ordered the review last Friday. A spokeswoman said the minister wanted the review completed as quickly as possible.

An Iarnrod Eireann board committee is to be established to oversee the investigation, and will retain independent advisers to assist. The company confirmed the viaduct was inspected twice last week, and that it stood over the quality of those inspections.

A full bridge inspection was also carried out in October 2007, with the next scheduled inspection in October this year.

Independent engineers also inspected the viaduct for scour -- or structural damage caused by water erosion -- in 2006 and no issues were raised

The next scour inspection is scheduled for 2012.

Last night Labour's transport spokesman Tommy Broughan called for a full review of the inspection regime, saying that if the bridge passed two inspections last week than there was something wrong with the system.

Investigations

There are now three separate investigations under way. The Rail Accident Investigation Unit is charged with establishing the cause of the incident, but it does not attribute blame or liability.

Iarnrod Eireann is conducting a separate inquiry, while the Railway Safety Commission will investigate if safety standards were complied with in relation to maintenance and inspection schedules.

Over €1.1bn has been spent upgrading the rail network under two railway safety programmes over the past decade.

- Paul Melia