25.01.16
RAIB to investigate post-storm responses to Lamington Viaduct
The Rail Accident Investigation Branch (RAIB) has launched an investigation into Network Rail’s actions and processes after Storm Frank’s destructive impact on the Lamington Viaduct last month.
The viaduct in South Lanarkshire was left battered just after Christmas when exceptionally heavy rain weakened one of its piers. According to RAIB, several trains passed over the structure after the ground beneath a pier had been eroded by a river scour on the morning of 31 December.
A driver initially reported a dip in the track, after which signallers restricted the usual 120mph speed of trains until maintenance staff arrived. After inspecting the track, workers removed the speed restriction and remained on site to carry out minor remedial work.
But after observing “unusual track movement” less than an hour later, staff immediately re-imposed the temporary speed restriction in both directions. They then blocked the line to all trains just a few minutes later after noticing a large crack in the second pier, one of the three viaduct piers in the river.
Although there was no damage to trains, the viaduct, which runs across the River Clyde between Carstairs and Lockerbie, was left seriously damaged.
Subsequent investigation revealed a large hole underneath the second pier and damage to three of the steel bearings that support the bridge deck.
The damage, initially underestimated, was soon discovered to be severe, forcing Network Rail to close off that whole section of the West Coast Main Line until the beginning of March.
As well as Network Rail’s own inspection of the structure, RAIB will independently investigate what actions were taken in response to a scour risk assessment carried out for the viaduct in 2005, as well as what was done when the Storm Frank warnings of exceptionally heavy rain in the region were issued.
The rail investigator will also look into the responses to the driver’s report of a track dip on the viaduct, the effectiveness of Network Rail’s processes intended to mitigate risks to structures due to extreme weather (including scour-related risks) and any underlying management factors behind the disaster.
Meanwhile, all TOCs operating services on the WCML are cooperating to ensure passengers and freight can keep moving, with temporary timetables and arrangements already in place.
Over the coming weeks, engineers will install extra concrete supports on either side of the damaged second pier before installing more 8m-long rock anchors and mini piles through the foundations.
The third pier will also undergo structural repairs and the course of the river will be widened to reduce future water pressure on the viaduct, all before the steel bearings are replaced, the viaduct bridge-deck realigned and the track re-laid.