‘Expensive’ Crossing ice prevention was dumped
TRANSPORT bosses have revealed plans for an “expensive” ice prevention system for Scotland’s showpiece road bridge – which was built
£245 million under budget – were dumped to save money.
The admission comes less than four weeks after falling ice shut the £1.34 billion Queensferry Crossing connecting Edinburgh and Fife for the second year running.
The Crossing, the biggest infrastructure project in Scotland in a generation, was shut for four hours on December 4, but only after patrol staff noticed ice falling.
And yesterday it emerged that Scottish Government-funded Transport Scotland has reviewed bridges across the world as part of efforts to prevent ice forming on the Crossing.
In a letter to Labour MSP Alex Rowley, Transport Scotland’s director of roads Hugh Gillies said that any viable solution would have to be “bespoke” as there was “no off-the-shelf solution”.
When it opened to traffic in August, 2017, the Queensferry Crossing was heralded by First Minister Nicola Sturgeon as “a symbol of a confident, forwardlooking Scotland” and a “feat of modern engineering”.
Before it opened, bridge operators said the 3.5 metre high
wind shields, would “almost entirely eliminate the need for closures”.
Transport Scotland’s road maintenance contractor Bear Scotland has admitted that ice prevention measures were not incorporated into the design of the bridge because of the expense.
The bridge came in £245m under budget, although it was completed eight months later than first estimated.
Ice on the cables was considered as a “potential issue” during the design of the bridge, but Bear Scotland said it was expected to be a “relatively rare event” with the climate experienced at the Forth.
“Rather than investing in an expensive preventative system that may only rarely be required, it was therefore decided to manage any ice accretion incidents through operational measures – ie by closing the carriageway on the rare occasions it occurred,” said Bear.
In November, after new ice sensors were installed, Transport Secretary Michael Matheson suggested the administration had learned a lesson from last winter when the crossing was closed following reports of ice falling on vehicles. Bear Scotland said that a number of system of weather sensors meant it could “monitor and respond to the specific weather conditions that we know can cause ice to form on the cables”.
And it said that its understanding of the phenomenon “should continue to improve, as the weather sensors gather data from future incidents”. But it admitted that it cannot prevent ice from forming on the crossing. “Our long term goal is to develop a solution that will prevent ice from forming on the cables, and the better we understand the conditions that cause this issue, the greater our chances of success,” said Bear.
“Every bridge has different design details and operates in a different climate, so there is no off-the-shelf solution that is suitable for the Queensferry Crossing – any such solution will be bespoke.”
According to original contractor information, there was already a multi-million pound real-time sensor system with 2,300 installed. These include anemometers to measure wind, barometers, rainfall gauges, air temperature and humidity sensors.
Details of the “innovative” system also referred to having structure temperature sensors for the steel, concrete, asphalt and stay cables, and “accelerometers” to monitor any movement or vibration. But Transport Scotland confirmed that the system was not expected to be fully operational until later in 2020.
In February, after another ice fall, Scottish Conservatives criticised ministers for failing to address the issue earlier, saying that “one of Scotland’s most critical transport routes exposes an SNP government in the throes of capitulation”.
Bear said that new ice sensors would allow it to monitor the four weather conditions that it is known can cause ice build-up and would “help to give us early warning of such conditions and allow us to more accurately measure and understand the conditions under which any future incidents occur”.
Bear added: “It is important to note that ice accretion will still be managed by closing the bridge should it happen again in the way that it has previously.”
In a response to the latest ice fall, it said it is confident that it can understand the parameters within which the problems with ice can occur “and we hope to refine this understanding with the help of the new weather sensors on the bridge”.
It added: “But the Queensferry Crossing has only been open for three years, so it is possible that there could be other weather conditions, not yet experienced, which could cause ice to accrete in a different way.” It said the phenomenon has occurred during a “particular combination of weather conditions, when wind speed and direction, temperature, dew point and relative humidity all converge within specific parameters”.