The bill for hired help to pick up the bins during last summer’s strike is expected to hit £1.6million for just three months.
For more than 222 days residents endured the prospect of their trash not being collected or their streets being piled high with bags.
Even though the dispute ended in November, payments are still being processed and costs have not yet been finalised.
According to a “high level legal assessment”, the bill is estimated at £1.6million between July and the end of September, specifically for the extra contractors involved.
The unions and city council came to an agreement ending the dispute after the saga left a total £6.6 million hole in the local authority’s finances, which will have to be met from a rainy day fund.
Piles of bin bags had lain strewn across city streets for weeks until the refuse workers’ union, Unite, agreed to accept a deal they had been offered by the council.
The dispute erupted over the council’s plans to “modernise” the service and save £5million a year, with opponents attacking the “downgrading” of 113 jobs and potential loss of pay.
The council, responding to a Freedom of Information Act request, said: “The costs of the industrial dispute have developed and evolved as the contingency plans were developed.”
A Birmingham City Council spokesperson said: “The cost of the industrial dispute last year is well documented, having been reported at November’s full council meeting and the subject of a number of articles in publications including the Birmingham Mail.
“With the matter now resolved, our focus is on working with employees and unions to develop a modern waste service which is more productive, effective and efficient, so we provide the standard of service that citizens rightly expect and deserve.”