Repair work to the Magdalen Street flyover was more than £400,000 over budget, it has been revealed.
A total of £310,000 was set aside for the work in Norfolk County Council's transport asset management plan, which was approved in April 2017.
But it has emerged that the repairs ended costing more than double that figure, coming in at roughly £753,000.
Norwich Highways Agency Committee chairman John Fisher said the phasing of the work resulted in increased costs.
He said: 'The nature of concrete repairs is such that it isn't possible to determine the full extent of repairs, particularly depth of repairs, until the defective concrete has been broken out.
'The works were carefully phased so that, for example, some repairs would be carried out on one pier and then repairs would be carried out on another pier and then back to the first pier.
'It is this phasing which extended the contract duration and led to the significant increase in cost.'
Mr Fisher said the work contract also included a constraint in regard to the amount of concrete which could be broken out from each column at any one time.
'This was for safety reasons,' he said. 'To avoid the columns being weakened to an extent that their load carrying capacity was compromised.
'This was particularly important bearing in mind that the structure continued to carry live traffic throughout the contract.'
He told the highways committee on March 22 this year that while the work 'exceeded the initial budget estimate', it was fully funded within the existing bridges maintenance budget.
The information was made public thanks to a question by Norwich resident Tony Clarke during the meeting.
Mr Clarke said he was curious to know the figure due to previous overspends on work carried out to the flyover.
In 2004 we reported how traders on Magdalen Street were demanding compensation following delays to the structure's repair.
Work had been due to take six months, but it ended up taking more than a year to finish.
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