The massive project is by far the biggest and most complex flood protection scheme in Scotland, involving risk of flooding from three local rivers as well as the Forth estuary in an area that includes a major port and an oil refinery.
With an initial budget of £200m, the most recent estimates now suggest that the project’s final costs are most likely to be anywhere between £420m and £650m.
Members of Falkirk Council’s executive have heard that the estimate cannot be any more accurate as the outline design work is still yet to be done.
However, an agreement is still needed on just how the work will be paid for.
At the moment, the national agreement is that the Scottish Government will pay 80 per cent of the costs with local authorities contributing the other 20 per cent.
But the scale of the Grangemouth project – which dwarfs the others – means even one-fifth of such a price would run into tens of millions and the council has asked that a new funding mechanism be found to make it more managable.
The council insists that the impact of a significant flood event on any of the critical infrastructure sites – such as the port or the refinery – could be devastating for both the national economy as well as local people.
Alistair Dawson, from Falkirk Council, said that the benefits of the scheme are clear and that he has no doubt the work is essential.
He told councillors: “I think it’s essential that between Falkirk Council and the Scottish Government we do find a mutually acceptable funding model.”
There have been calls for the industries who will benefit – including Forth Ports and Ineos – to pay some share of the cost.
Council leader Cecil Meiklejohn said that discussions are currently ongoing with local businesses through Grangemouth Future Industries Board about how they might contribute.
She said: “One of the key reasons for setting up that board was for discussions of this magnitude, so we do have business at the table.
“I think it’s recognised by government that the 80/20 split would be an unfair burden to put on a single local authority.
“It’s going to take time to work through all of that but we are having active conversations with all the stakeholders.”
While it is called the Grangemouth Flood Defence Scheme, it actually takes in several other areas across the Falkirk district.
Conservative councillor Lynn Munro questioned whether the risk that the town is facing is really worth the sum of money involved.
Mr Dawson said: “When you break it down metre by metre, we’re on comparable costs with other areas.
“You ask if it’s essential – but the flipside is what the cost would be of not doing the project.”
Despite the funding headache, work is still expected to go ahead as planned sometime in 2025.