Inquiry focuses on seabed erosion
EROSION OF the seabed under the Broadmeadow Estuary rail viaduct has been identified as the primary line of inquiry into its partial collapse, according to a preliminary assessment by Iarnród Éireann.
While not excluding other factors or possibilities, the investigation by engineers and other experts “centres on a recent and significant erosion of the seabed in the vicinity of the pier involved in [last] Friday evening’s incident”, the company said.
“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.
“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,” Iarnród Éireann’s said.
The continuing investigation will examine “all other factors” relating to the viaduct, including tidal issues in Broadmeadow Estuary, rainfall and climatic issues as well as inspection of maintenance reports and procedures, with an input from all relevant personnel.
Iarnród Éireann said it would “immediately establish” an inspection team, assisted by independent advisers and overseen by a board committee, to inspect bridges and viaducts across areas of running water throughout the entire rail network.
Referring to last Tuesday’s inspection of the Broadmeadow viaduct by an engineer, it said this was “specifically a visual examination of the condition of the piers as visible above water, to ensure that any markings were cosmetic and not structural in nature”.
The inspection confirmed this, and Iarnród Éireann was “completely satisfied that the inspection was thorough, professional and accurate”. A track-monitoring vehicle had also travelled over the line last Thursday and no deviations from normal conditions were recorded.
The Broadmeadow viaduct’s last biannual inspection was carried out in October 2007 and the next such inspection was scheduled for October of this year. A separate inspection to assess water scouring and associated issues was carried out in 2006.
Iarnród Éireann said this inspection had been undertaken by independent specialists. “The outcome of this inspection was that no scour issues had arisen, and [it recommended] that the next scour inspection be scheduled for 2012.”
Labour Party transport spokesman Tommy Broughan TD called yesterday for a full review of Iarnród Éireann’s procedures for inspecting rail lines in the light of the collapse of the Broadmeadow viaduct.
The general manager of Translink, the Northern Ireland company which jointly runs the Belfast-Dublin Enterprise service along with Irish Rail, said yesterday he believed it would take up to six months for full services on the route to run again.
But Iarnród Éireann spokesman Barry Kenny said it was still sticking by its three-month time frame to replace the viaduct.
“At this point in time we would say six months is a bit pessimistic. It is our personnel that are on site and that is our own engineers’ best estimates – three months.”
He said the rail operator was pleased with the first day of operations yesterday where replacement bus services were put on routes affected by the collapse.
There will be one significant change from today. Direct buses will operate from Balbriggan to Dublin city centre. Yesterday people had to travel from Balbriggan to Skerries by train and then get a bus into Dublin.