The £1.4bn Queensferry Crossing will not be completed until May 2017, five months later than expected.
Scottish Government economy secretary Keith Brown said the bridge across the Forth Estuary would not be completed by the target of December 2016 because of bad weather hampering construction.
The contractual completion date for contractor consortium Forth Crossing Bridge Constructors (FCBC) is June 2017, and completing the project six months earlier was considered challenging but achievable.
However, a statement by Transport Scotland said that FCBC had since advised that this was no longer possible.
Transport Scotland said: “Since September 2015 the downtime due to adverse weather, specifically wind, has been 40% compared to the 25% anticipated by the contractor. Until May, FCBC believed that they could mitigate these effects. However, the impact of the weather in April and May with 13 days and 12 days lost to weather was such that they have advised that they can no longer deliver the December 2016 target.
“Whilst FCBC have been able to mitigate the impacts of weather by increasing resources and running a number of activities in parallel they are now entering a stage of bridge construction which is technically very complex.”
It added: “In order to mitigate the ongoing weather impacts that have arisen over the past few months, FCBC has procured additional physical resource, increased staffing by taking on an additional 100 workers, increased working hours, altered construction methodologies where possible and challenged critical construction sequences to identify where any programme efficiencies could be found.
“They have now reached the stage where further additional resources will not bring the delivery date forward due to the complex technical nature of the construction work. Specifically the bridge deck and the cable installation process which began in September 2015 is particularly sensitive to wind and this increases as the cables used become longer and are installed at a greater height.”
Brown said: “We will continue to work closely with the contractors and I will personally ensure that every pressure and every resource is brought to bear to deliver or even better the revised target date of May 2017.
“We have always been ambitious about this project and have always worked towards a deliberately ambitious target. However, It is important to recognise that FCBC still fully expects the project to complete within the timeframe of their contract. This project is not late and there will be no impact on the public purse,” he added.
Speaking to CM in April 2015, Andrew Price, marine liaison manager for the FCBC consortium, who relays weather forecasts to the construction teams, said that the consortium was using a number of Met Office forecasting packages to try to keep the work on schedule.
