Officials say the new road bridge over the Forth will still be completed on time despite delays in the construction process last year.
Government agency Transport Scotland has confirmed Forth Crossing Bridge Constructors (FCBC), the international consortium building the Queensferry Crossing, encountered “challenges” with foundation work.
They say FCBC has changed some of its plans to make up for lost time and the £1.45bn project will be ready, as planned, by the end of 2016.
Transport Scotland’s project director David Climie said: “Yes, they have had some challenges, particularly with excavation of material from the south tower, where they’re going down to 40m below sea level.
“They also had some issues getting the rock sufficiently clean to make sure there was the full contact between the underwater concrete and the rock, but that’s a fundamental principle that has to be right in order to be able to progress.
“Even with those challenges we’re still absolutely on track for completion by the end of 2016.”
The new structure will be the second longest cable-stayed bridge in the world. The roadway will be attached by cables to three towers, each more than 200m high.
A 28m high section of the central tower can now be seen rising from its base on Beamer Rock in the middle of the Forth, but as yet there is no visible sign of the south or north towers.
Transport Scotland says the project is at the halfway stage, and much of the work is still being done out of sight, within the huge metal caissons from which the north and south towers will rise.
They’re predicting the three towers will reach “deck height” this summer. The decks will carry the roadway and the task of attaching them to the towers is expected to begin in the autumn.
“I think any contractor would always like to be further ahead than they are,” said Mr Climie. “On the south tower things have not gone as perfectly as they would have liked.
“What they’re going to do differently is that originally they were going to build out from two of the towers with the deck first, and then follow up with the third tower. What they’ve done to pick up some time, which they’ve decided they need to do, is to build out from all three towers simultaneously. That’s a relatively low cost issue to deal with. From a fundamental point of view as a contractor, it’s an easy fix.”
“It’s not keeping me awake at night. When they’ve encountered problems, they’ve responded absolutely correctly, and that gives me great confidence that we will be able to achieve the end-of-2016 date.”
Alan Simpson, former chairman of the Institution of Civil Engineers in Scotland said: “A programme is always being updated as you go along. You can never say it’s always going to be done in accordance with the original programme. That doesn’t necessarily mean that if one part of the project is late, the whole project is in jeopardy.”