Thame's swimming pool is running over budget before even the first hole has been dug.
But hopes are still high that on completion next year there will be cash back for both the council and the contractors.
A special meeting of the full council was told the original £4.3m is not going to be enough.
Nigel Jones, of Wilmott Dixon Construction, said the estimate was given nine months ago and costs for electrical and other work were going to be far higher than expected.
An agreed maximum price has still to be worked out and is now expected to be more than £4.5m.
Another problem is that the new health and fitness suite, to be paid for by South Oxfordshire District Council with £1.48m, is over budget as well. The aim was that it would be completed under budget and the town council would get anything left over.
Now it is £341,000 over that figure.
The first phase of the car park - the work being done currently on the Thame sports and arts centre site - has come in with a £24,000 saving.
The town council decided there must be no delays to the September 10 start on both the pool and the fitness suite.
Mr Jones promised that at every stage of the work costings would be kept under review to come in under the final agreed price. He said anything left over wouldl be split 50-50 between the council and his firm.
Town council member Mike Le Mesurier, who started off the latest campaign for a pool ten years ago, said he was not surprised at the costs. He said: "We are going to have a top class pool and these costs will be met - it simply cannot be done on the cheap."
The pool is being funded from £7.2m the council was paid for selling recreation land for housing.
The remainder is being invested to pay for running costs and maintenance.
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