MSPs have been told it will take time to find a permanent solution to prevent ice from building up on the Queensferry Crossing.
Mark Arndt from the Amey Forth Bridge Operating Company said work was being carried out to discover “permanent viable solutions” to the problem – which resulted in the £1.35 billion crossing being closed to all vehicles for two days.
The bridge was shut to traffic after ice that had built up in wintry weather conditions fell from the cables, damaging eight vehicles.
Ms Arndt said: “We are also actively looking for permanent viable solutions to mitigating ice forming in the first place, that will take time through research and development and the like.”
He spoke as MSPs on Holyrood’s Rural Economy and Connectivity Committee questioned Transport Secretary Michael Matheson and bridge officials about the closure.
Labour transport spokesman Colin Smyth told them: “It is clear that there is a problem here you haven’t got a solution to yet.”
While enhanced monitoring arrangements have been put in place on the bridge for safety so it can be closed again if there is another ice build up, the Labour MSP said: “That is clearly not what people want to happen, we want to find a solution that will actually stop the bridge requiring closure.”
Mr Arndt said “various options” were being considered, including the possibility of coating the cable sheaths on the crossing with a hydrophobic material to repel water or installing heating mechanisms.
Mr Matheson told the committee: “There isn’t an off the shelf solution for bridges that experience this problem.
“International experience would say that very often they have to look for bespoke methods in order to address this, specific to the bridge and the circumstances they are experiencing.”
He told how problems arose last week when a “squall of sleet, icy weather was coming in”, resulting in ice building up on the bridge and then falling off the cables “very quickly”.
The Transport Secretary has already announced ice sensors are being installed on the crossing in the coming months to help detect any build-up.
But with the problem having also affected the crossing in March 2019, he hit back at suggestions that little had been done.
While the issue of ice build-up only happens in a “very limited weather environment” Mr Matheson said a “significant level of work” had been carried out since the problem was first identified.
He told MSPs: “I refute any suggestion that nothing has been done or little has been done since March last year, that would be a gross misinterpretation of what has been undertaken and the very challenging nature in which the engineers have had to try to pinpoint the nature of where the ice is coming from and also the circumstance in which it occurs, because it only occurs in certain circumstances.”
The Transport Secretary added while the closure of the bridge was “unexpected and most unwanted”, engineers had used the period to “better understand the circumstances that give rise to this problem”.
Committee convener Edward Mountain pointed out that problems with ice had occurred on similar bridges in countries such as Canada, Norway, Sweden, Japan and the US, as he questioned why ice sensors had not been included in the original specification for the Queensferry Crossing
But Laurence Shackman, the Queensferry Crossing project manager for the design and construction phase, said at the time the plans were being drawn up “there wasn’t any common ideal solution to get rid of the problem”.